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Reverse Osmosis Systems
Old 11-08-2014, 08:56 PM   #1
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Reverse Osmosis Systems

Yeah, I know they 'waste water', but I'm still thinking about putting in one of these systems...under sink style. I'd really like to eliminate the chlorine and stuff in my city water. This is a health concern for me.

My main thing is ongoing supplies costs. They all probably have a similar waste to good water ratio (and water is pretty cheap, so a slight change in the ratio is not a big deal). But it seems like the supplies to keep it going can be the deal breaker. It's a bit like the printers...the printer is $49, but the printer cartridge is $109!

Does anyone have background on what's being sold nowadays and how much the system versus the upkeep is?
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Old 11-08-2014, 09:18 PM   #2
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I don't remember how much our system cost 7 years ago, but I put new filters in every couple of years at about $75 per. According to the water company we should do it every year, but we're snowbirds so it sits dormant half of each year.

Our well water (treated) is pretty decent, but the water from the RO system is excellent. DW uses it for the 6+ cups of tea she drinks every day. I use it for my Soda Stream, and for drinking water. We use the regular well water for cooking and for the dogs.

I know they are supposed to be wasteful, and maybe they are out in the parched western lands. But here on the Eastern Shore of MD water is plentiful, and whatever is "wasted" just goes right back into the water table. We love it.
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Old 11-08-2014, 09:24 PM   #3
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I'd do some research before committing.

A good RO system will remove all the minerals and some of those may be beneficial for your body. And (I have read this) some pesticides and other dissolved chemicals won't be filtered out. The last RO water I tasted from a very expensive industrial system was kind of bland.

There are a ton of articles out there on RO systems and their pros and cons.

Good luck!
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Old 11-08-2014, 10:20 PM   #4
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If chlorine is what worries you, then you don't need an RO system.

Your city water has chlorine in it, and you need to remove that chlorine >before< it would get to any RO membrane anyway (because it will destroy the membrane rather quickly). The typical setup would be:
city water -> sediment filter (to reduce silt that would jam up the following filter) --> granulated activated carbon (GAC) filter (to get rid of the chlorine and organic chemicals (e.g pesticides, etc) --> drinking water tap (and ice maker). You could put an RO membrane after the carbon filter, it will remove some things that the other filters won't (esp dissolved inorganic minerals, like salt, etc--could be important if you have a water softener). You could even install a UV light downstream of that to kill viruses and bacteria--but the city's chlorine will have done that already, the only other source would be a colony in your carbon filter--that's a good reason to change them annually.

If you go with a simple sediment and granulated carbon filter, your drinking water will taste about like it tastes if you use a Britta filter--which most people find to be very good. If you are on a typical city water system, this is all you need. The cost of the sediment filter (replace every 6 mos) and a good granulated carbon filter (replace annually) will be less than $75 total per year, which is quite a bit cheaper, more convenient, and better for your health and the environment than bottled water.

I'm on a well with hard water, and I built quite a complicated system: water softener, sediment filters, carbon filter, RO, polishing filter, UV light. The drinking water tastes great. If you are on city water you don't need to go to all that trouble--the city has done most of the work for you. If you haven't already done so, get a report from your city and see what is actually in the water--they have to tell you.

Lastly--the brand of sytem you buy will have a big impact on the cost of supplies (remember--what you asked about!). Some newer systems have convenient (and propietary) filters in which the filter body and the internal media are all disposable. Remove the old one with a quarter-turn, insert the new one with a quarter turn and you are done. It takes just a minute or two. My system uses filter bodies that are permanent: I unscrew them with a big plastic wrench, dump out the old filter cartridge, clean them out (soap and a bit of bleach), clean out the top of the housing into which they screw, insert new filter media into the body, put some lube on the O-ring, and screw them into place. The filters for these are standard, generic, and widely available, they cost about 1/2 what the fancy (and more convenient) proprietary filters cost. It takes me about 30 minutes, start to finish, to change two filters, so that's an hourly rate of about $75/hour (after taxes). As a bonus, I'm much more certain that these filters will still be available as long as I need them.
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Old 11-09-2014, 12:27 AM   #5
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I have no personal experience with RO, but have experience with Chlorine via faucet and pool

All water around here is city water via large water utilities, and the source is surface water (reservoirs). And with surface water in a warmer climate, quite a bit of Chlorine is used, especially in late summer when the water temp is the highest. Turn on a faucet with an aerator then, and you smell Cl. Lift the lid on a toilet, and you smell Cl. And in the worst time of the year, strong Cl taste. Runs at least 1 PPM as tested at the faucet with pool test kit. I am not comfortable drinking it with that level of Cl.

So... refrig has cartridge filter with carbon for the water through the door and ice. We can tell by taste when the filter has absorbed its fill, it's long after the filter time monitor has said to change it out.

Most of my day to day drinking water comes from my own simple setup: I fill a wide-mouthed one gallon pitcher at the kitchen faucet with the faucet set to multi-stream to pump in as much air as possible. Then I leave it sit out on the counter for a couple days to let the Cl evaporate out. Then pour it into a gallon jug in the refrig, which I use from.
I found from experimentation (and also in-ground pool experience) that Cl evaporates out of water quicker the higher the temperature, and the more surface area exposed to air. Makes sense. Solubility of a gas in a liquid.

Water used in cooking usually comes straight from the faucet, the heating of it when cooking drives out the Cl fast.

Most of the TTHMs (Total TriHalo Methanes, by-products of disinfection using Cl) have high volatilities, so I figure they are evaporating out too. Our water meets the federal standard for max TTHM, but they are not nice chemicals. But better than bacteria.
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Old 11-09-2014, 02:01 AM   #6
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Quote:
Originally Posted by samclem View Post
If chlorine is what worries you, then you don't need an RO system.

Your city water has chlorine in it, and you need to remove that chlorine >before< it would get to any RO membrane anyway (because it will destroy the membrane rather quickly). The typical setup would be:
city water -> sediment filter (to reduce silt that would jam up the following filter) --> granulated activated carbon (GAC) filter (to get rid of the chlorine and organic chemicals (e.g pesticides, etc) --> drinking water tap (and ice maker). You could put an RO membrane after the carbon filter, it will remove some things that the other filters won't (esp dissolved inorganic minerals, like salt, etc--could be important if you have a water softener). You could even install a UV light downstream of that to kill viruses and bacteria--but the city's chlorine will have done that already, the only other source would be a colony in your carbon filter--that's a good reason to change them annually.

If you go with a simple sediment and granulated carbon filter, your drinking water will taste about like it tastes if you use a Britta filter--which most people find to be very good. If you are on a typical city water system, this is all you need. The cost of the sediment filter (replace every 6 mos) and a good granulated carbon filter (replace annually) will be less than $75 total per year, which is quite a bit cheaper, more convenient, and better for your health and the environment than bottled water.

I'm on a well with hard water, and I built quite a complicated system: water softener, sediment filters, carbon filter, RO, polishing filter, UV light. The drinking water tastes great. If you are on city water you don't need to go to all that trouble--the city has done most of the work for you. If you haven't already done so, get a report from your city and see what is actually in the water--they have to tell you.

Lastly--the brand of sytem you buy will have a big impact on the cost of supplies (remember--what you asked about!). Some newer systems have convenient (and propietary) filters in which the filter body and the internal media are all disposable. Remove the old one with a quarter-turn, insert the new one with a quarter turn and you are done. It takes just a minute or two. My system uses filter bodies that are permanent: I unscrew them with a big plastic wrench, dump out the old filter cartridge, clean them out (soap and a bit of bleach), clean out the top of the housing into which they screw, insert new filter media into the body, put some lube on the O-ring, and screw them into place. The filters for these are standard, generic, and widely available, they cost about 1/2 what the fancy (and more convenient) proprietary filters cost. It takes me about 30 minutes, start to finish, to change two filters, so that's an hourly rate of about $75/hour (after taxes). As a bonus, I'm much more certain that these filters will still be available as long as I need them.
+1
samclem nailed it.
Our daughter has hard water in her 'new' house in Tucson and the pipes are pretty limed up. I am looking at filter plus GAC filter plus a water softener for her. I can do that for her myself (engineer with a small history in water treatment).
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Old 11-09-2014, 06:10 AM   #7
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As samclem noted, a carbon filter should do the job nicely for you, and be much cheaper and simpler. It will get the chlorine taste out of the water, which is what you really want. Almost all breweries that get city water use a simple carbon filter for this reason, and it works fine for them.
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Old 11-09-2014, 09:15 AM   #8
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+1 (2-3-4-5? I lost count) to what samclem said. For chlorine, a charcoal filter does the job.


But I need to clarify a point regarding chlorine and chloramine (commonly used today, as it is more stable)...

Quote:
Originally Posted by Telly View Post
....
Most of my day to day drinking water comes from my own simple setup: I fill a wide-mouthed one gallon pitcher at the kitchen faucet with the faucet set to multi-stream to pump in as much air as possible. Then I leave it sit out on the counter for a couple days to let the Cl evaporate out. Then pour it into a gallon jug in the refrig, which I use from. .... .
Chloromine - definition of Chloromine by The Free Dictionary

Quote:
chloramine (klr-mn)
1. One of three bactericidal compounds that form when chlorine and ammonia react in water. Chloramines are used to purify drinking water, since they are more stable than chlorine and produce fewer harmful by-products. ...
When brewing beer, chlorine/chloramine can cause off-flavors. Home brewers use charcoal filters or 'campden tablets' (potassium or sodium metabisulfite), which immediately break the chlorine compounds in to (IIRC) ammonia and that evaporates almost immediately, and/or isn't a problem at low ppm levels.

So if your supplier uses chloramine (likely), just sitting out or boiling won't be very effective.

-ERD50
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Old 11-09-2014, 09:41 AM   #9
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As samclem noted, a carbon filter should do the job nicely for you, and be much cheaper and simpler. It will get the chlorine taste out of the water, which is what you really want. Almost all breweries that get city water use a simple carbon filter for this reason, and it works fine for them.
When I brew, I go buy RO water for $0.30/gal out of the Glacier machine, which is a stand-alone RO water dispensing machine hooked to the city supply at our local grocery store.

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Originally Posted by samclem View Post
...
My system uses filter bodies that are permanent: ... they cost about 1/2 what the fancy (and more convenient) proprietary filters cost.
...
That's good info there, thanks. I thought they all were proprietary.

As to whether to do RO or carbon filter, maybe you all have a point. Here's my water profile (surface water treated by the city):

Code:
Total Coliform (% positive) 0.19% monthly average, 0.66% highest monthly average (EPA limit: 5% postive per month)
Turbidity (NTU) 0.10/100% (EPA limit: 0.3)
Fluoride (ppm) 0.69 (EPA limit: 4)
Copper (ppm) None detected at 90th percentile (EPA limit: 1.3)
Lead (ppb) 7 ppb detected at 90th percentile (EPA limit: 1.5)
Lead: 3 of 53 sites exceeded Action Levels
Chlorine (ppm) 1.30 (EPA limit: MRDL=4)
THM (ppb) 59.7 (EPA limit: 80)
HAA5 (ppb) Haloacetic Acids 17.3 (EPA limit: 60)
Total Organic Carbon (ppm min-max) 1.01 - 1.64 (EPA limit: 2.0)
Strontium (ppb) 30 
Vanadium (ppb) 0.65
Chromium, Total (ppb) 0.30
Chromium-6 (ppb) 0.073
It looks like lead is a problem sometimes, but as I understand it, the testing comes from taps inside houses, so is subject to the house's supply line contamination. My house was built in 1993 and has copper supply lines.

I don't know what the health effects are for all of those other minerals at low concentrations. Might it be better to be safe than sorry?

Water is our household's primary beverage, so I figured getting the best, healthiest water is probably a good idea. I don't mind paying the price for the system and for the ongoing supplies, I just don't want to select a system where I end-up overpaying for the ongoing supplies.
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Old 11-09-2014, 09:55 AM   #10
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Municipal water suppliers can only give you broad average ranges for the things they measure. If you're really interested, you can get a comprehensive analysis of your own tap water from a number of laboratories for very little money.

Here's the one I've used for years:
https://producers.wardlab.com/default.aspx
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Old 11-09-2014, 11:02 AM   #11
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...

Lastly--the brand of system you buy will have a big impact on the cost of supplies (remember--what you asked about!). ... My system uses filter bodies that are permanent: I unscrew them with a big plastic wrench, dump out the old filter cartridge, clean them out (soap and a bit of bleach), clean out the top of the housing into which they screw, insert new filter media into the body, put some lube on the O-ring, and screw them into place. The filters for these are standard, generic, and widely available, they cost about 1/2 what the fancy (and more convenient) proprietary filters cost. ...
samclem, what brand do you have? Mine (An old Spectra-Pure model, designed for aquariums) takes the generic charcoal carts (~ $7, change every 3-6 months). Have never needed to change the RO filter itself, still good after ~ 17 years.


I purchased one designed for use with an aquarium for several reasons. It is the same type of unit, minus the pressure tank. I just have it dump into a 5 gallon tank with a spigot.

PLUS: Cheaper initial $ w/o the tank.

PLUS: Wastes less water, it works more efficiently when it does not need to work against the pressure in the little supply tank.

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Old 11-09-2014, 12:46 PM   #12
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samclem, what brand do you have? . . .
Sorry, I dunno. I bought the setup online, it was very similar to the systems sold by these guys (and many others). I bought the 5-stage RO system with tank ($199), and added a permeate pump (?about $100?) and a UV light system (??about $100??).
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PLUS: Cheaper initial $ w/o the tank.

PLUS: Wastes less water, it works more efficiently when it does not need to work against the pressure in the little supply tank.
That would work fine for most uses. Our system is in the basement (very convenient--easy to get to everything and the purged water keeps my floor drain traps wet!). I needed the tank because the water goes to a tap at the sink and it also feeds our icemaker. As an aside, it's important to have a good flow rate if the water is going to an icemaker, since the solenoid in the icemaker is powered up as long as it takes to fill the tray. Lower flow rate-->longer solenoid "on" time-->shorter solenoid life.
The permeate pump is an add-on that uses the effluent from the RO process to push the new water into the ROhousing, a bit like a turbopump in a car. If your line pressure is low (mine is about 50-60 PSI), it helps increase the RO output and significantly reduces water waste. A similar thing can be accomplished with an electric booster pump, but the permeate pump has proven very reliable for us.

Sengsational: Notes in bold are mine. GAC = granular activated carbon
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Lead (ppb) 7 ppb detected at 90th percentile (EPA limit: 1.5)
Lead: 3 of 53 sites exceeded Action Levels
You can buy GAC cartridges that also work against lead.
Chlorine (ppm) 1.30 (EPA limit: MRDL=4) GAC will reduce this a lot
THM (ppb) 59.7 (EPA limit: 80) GAC will address these trihalomethanes
HAA5 (ppb) Haloacetic Acids 17.3 (EPA limit: 60)
Total Organic Carbon (ppm min-max) 1.01 - 1.64 (EPA limit: 2.0) GAC for this
Strontium (ppb) 30
Vanadium (ppb) 0.65
Chromium, Total (ppb) 0.30 You'd need an RO system to reduce this.
Chromium-6 (ppb) 0.073
You'd probably need to do some research and see how much these various substances are of concern to you, and what you'd need to do to reduce them.
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Old 11-10-2014, 12:23 AM   #13
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......But I need to clarify a point regarding chlorine and chloramine (commonly used today, as it is more stable)...

.....So if your supplier uses chloramine (likely), just sitting out or boiling won't be very effective.
-ERD50
Our WTP uses Chlorine. Chloramine is used once a year for only a very short period of time, and PSAs go out to advise in advance of it that though the water may have a "smell" or "taste" (yeah, ewww, icky pond water!) in the chloramine cycle, it is still "safe to drink".

In a pool, chlorine can combine with organic loads and create chloramines, which readily come out of solution to create that strong sharp "chlorine" smell (often overpowering in motel pool areas!). Which is the main purpose of shocking, to reduce chloramines.
In season I keep ours around 2 -3 PPM, which is on the high side, but there are less problems in the sun with warm water, since high gives a greater safety margin. And tends to prevent algae.
The only time I smell Cl is loading the chlorinator. I get everything set, and hold my breath from first opening pail, tablets out, pail cover back on tight, drop in chlorinator, screw lid back on, step to the upwind side, and finally breath again.

In winter with the floating cover on, I run it higher, maybe 6 - 8 PPM. I have to take 1/3 samples and dilute with tap water or distilled to check Cl, as the indicator goes orange not much above 3 PPM. By diluting, I can scale the measurement by keeping it in the indicator's working range.

In my experiments years ago, I put open pitcher into refrig, and days later it seemed to have just as much Cl in it as when I put it in. Cold temps, little Cl evaps out. Has to sit out on the counter for a couple days to get rid of it. Just like Cl amount required to maintain Cl level in the pool vs. water temperature.

If anyone wants to drink from my pool, go ahead. But no additions, please
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Old 11-10-2014, 04:33 AM   #14
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A few years ago I was on a plane and the guy next to me was some type of water expert that flew to different cities and worked on water filtration systems. I always wondered why the city I lived in didn't use just plain chlorine in the drinking water. He told me that when there is chloramine in water it has a high bacteria count or and fecal matter. I said oh great.

I have had a few Osmosis filters and they never lasted very long, cartridges are expensive, and the water tasted flat. Used it to make coffee and it was terrible. I just use the charcoal filter on the frig.
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Old 11-15-2014, 03:46 PM   #15
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I looked on Amazon, sorted by user rating and bought Apec Water "Essence" unit. I installed it today. The instructions were very detailed, so easy to install. The kit had everything, even teflon tape.

Uses industry standard sized filters, so that concern was addressed. It says that the silt filter and the 2 charcoal filters need to be changed every 6 to 12 months or I'll ruin the RO membrane. The RO membrane is supposed to last 2 or 3 years.
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Old 11-15-2014, 04:05 PM   #16
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I looked on Amazon, sorted by user rating and bought Apec Water "Essence" unit. I installed it today. The instructions were very detailed, so easy to install. The kit had everything, even teflon tape.

Uses industry standard sized filters, so that concern was addressed. It says that the silt filter and the 2 charcoal filters need to be changed every 6 to 12 months or I'll ruin the RO membrane. The RO membrane is supposed to last 2 or 3 years.
Great, that looks like a fine setup, and getting replacement filters should be easy and cheap. You might consider buying a small handheld total dissolved solids (TDS) meter (about $20) and using it to determine when to replace your RO membrane (you can buy one online, or maybe from a high-end aquarium shop). Chances are good that, if your carbon filters are effectively removing the chlorine from the municipal water, you'll get a longer life out of your RO membrane than 3 years (in my experience). You can use the TDS meter to tell you the amount of dissolved "stuff" in your city water, and the amount of dissolved "stuff" in your post RO water right now. If the water output from the TO or the amount of TDS rises too much (your call), it might be time to change out the RO membrane. If it lets you extend the time you use your RO membranes by even a year or two, the meter will have saved you some hassle and paid for itself.
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Old 01-15-2015, 11:03 PM   #17
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The permeate pump is an add-on that uses the effluent from the RO process to push the new water into the ROhousing, a bit like a turbopump in a car. If your line pressure is low (mine is about 50-60 PSI), it helps increase the RO output and significantly reduces water waste. A similar thing can be accomplished with an electric booster pump, but the permeate pump has proven very reliable for us.
Update: I Jinxed myself--the permeate pump died last week after 8 years of use. A new one was about $45. I replaced the RO membrane, too (after 4 years of use) and the new one is doing a better job of removing the sodium left by the water softener in the drinking water (TDS readings went from 290 PPM to 150 PPM).
Supplies and replacement parts for my fairly involved drinking water setup are costing about $100/year.
-- Every 6 mos: 1 sediment filter ($5) and carbon filter ($15)
-- Every year: UV light replacement ($10), inline polishing filter (carbon, $12)
-- Every 3-4 years: RO membrane ($70 = approx $20 per year)
-- Every 8 years: Permeate Pump ($45 = $6 per year).

For us, this works really well. Tastes as good and is a lot less expensive and more convenient than bottled water. If we were on city water and if we didn't need to remove the salt left by the water softener it would be even simpler/cheaper.
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Old 01-17-2015, 10:25 AM   #18
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.... I replaced the RO membrane, too (after 4 years of use) and the new one is doing a better job of removing the sodium left by the water softener in the drinking water (TDS readings went from 290 PPM to 150 PPM).
Supplies and replacement parts for my fairly involved drinking water setup are costing about $100/year.
-- Every 6 mos: 1 sediment filter ($5) and carbon filter ($15)
-- Every year: UV light replacement ($10), inline polishing filter (carbon, $12)
-- Every 3-4 years: RO membrane ($70 = approx $20 per year)
-- Every 8 years: Permeate Pump ($45 = $6 per year).

For us, this works really well. Tastes as good and is a lot less expensive and more convenient than bottled water. If we were on city water and if we didn't need to remove the salt left by the water softener it would be even simpler/cheaper.
I'm curious why you feel you need so many stages? I purchased a very simple unit way back in 1998, just a standard carbon filter cartridge and the RO membrane (15 GPD). I don't use a pressure tank (those reduce efficiency), I just let it drip into a 5 gallon container with a (gravity) tap on it, turn it on/off manually (since it takes ~ 8 ~ 10 hours to deliver 5 gallons), and I fill gallon jugs for the kitchen (better than hauling them from the store). This is essentially what the aquarium enthusiasts use.

We are also on a well, so the RO is mainly to remove the salt from the softener (which replaces the minerals & iron with sodium). I got one of those cheap TDS meters recently, and it still is indicating that my original membrane is working fine. I see ~ 600 ppm TDS on the tap water, and ~ 30 ~ 40 ppm on the RO. And that agreed with my rough observations of letting some of each evaporate in a clean glass (salt sediment in tap water, nothing visible with RO water), and trying to measure some uA current with a 9V battery (very roughly a 10x difference).

We only use this for coffee, tea, some drinking water and some plants. Maybe ~ 2 gallons per day. But 16 years still seems like a long life. IIRC, the guy at SpectraPure that I talked to at the time said I could expect ~ 10 years with that usage rate.

The only 'problem' I've had, is that by the recommended carbon filter change period (~ 6 months), I'd get some black bacteria build up, producing a stinky/skunky smell. But they recommend washing everything (but the membrane) with bleach solution when you change the filter. But then sometimes, I'd get the smell after just a couple months. Kinda a pain to change and clean the filters that often. But I think I found a solution...

Once every week or two, I disconnect the feed line (twists off by hand), and using a pipette to add about 10 drops of bleach in the line. Reconnect, then run it normally. That seems to be just enough bleach to keep the bacteria build-up at bay (we will see, I just started this a month ago, but it actually cleaned up the beginnings of a little odor, and it has remained odor-free).

I found that these membranes are rated for ~ 1000 ppm-Hrs of chlorine. My 10 drops might be getting me to maybe 10 ppm, but that should flush through in a few minutes, and the charcoal filter should absorb it anyhow. I think municipal chlorine levels are ~ 2 ppm, so 10 ppm for short while is a very low average.

But now I'm thinking - maybe one of those UV lights on the input of my system would keep things clear, and a little less work? Do they handle 60 psi pressures?

-ERD50
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Old 01-17-2015, 11:01 AM   #19
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Originally Posted by ERD50 View Post
I'm curious why you feel you need so many stages?
Guilty as charged. Your setup would work fine, but having the pressure tank allows us to feed the icemaker (yep--another complexity waiting to break down--tell it to DW) as well as the tap at the sink, and saves the turn on/turn off thing every day.

Our well water must be a lot harder than yours, so I'm seeing over 1300 PPM of (primarily) sodium after the water softener. After the RO< I'm at 165, which is okay, but I do wonder why it isn't lower. I suspect it is "TDS creep" caused by the on-off of the RO system (which would be improved with a system like yours--but that won't fly at our house --SWMBO )

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The only 'problem' I've had, is that by the recommended carbon filter change period (~ 6 months), I'd get some black bacteria build up, producing a stinky/skunky smell. . . .
Once every week or two, I disconnect the feed line (twists off by hand), and using a pipette to add about 10 drops of bleach in the line. Reconnect, then run it normally. That seems to be just enough bleach to keep the bacteria build-up at bay (we will see, I just started this a month ago, but it actually cleaned up the beginnings of a little odor, and it has remained odor-free).
I'd worry about how that might affect the RO membrane. They don't take chlorine well at all, which is why a carbon filter is needed before the RO when on city water (which typically has a very low chlorine residual by the time it gets to your tap--a lot less than your 10 drops of bleach). If the carbon is doing its job (removing the chlorine) then some bacteria will still be alive somewhere in that carbon filter media. If the carbon isn't totally removing the chlorine, then it is getting through to the RO membrane.

If you are using granulated carbon filters, I'd switch to carbon block (there's much less space for the bacteria to set up home). The UV units will have no problem with 60 PSI, but I'd recommend putting it very last in your treatment flow. As a practical matter, there's no hope of killing every single bacteria before it gets to the carbon element, so if you put the UV before the element and conditions are favorable, they'll be there in droves soon enough. Better to kill them on the way to your catch bucket--and it will kill 99+% of them. As a reminder, look for a UV system that takes regular (6 watt) bulbs as a replacement, not ones that require a proprietary replacement. The difference is about $20 per year. I'll try to find info on the unit I've got--it works well and is easy to service.
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Old 01-17-2015, 07:10 PM   #20
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Our well water must be a lot harder than yours, so I'm seeing over 1300 PPM of (primarily) sodium after the water softener. After the RO< I'm at 165, which is okay, but I do wonder why it isn't lower. I suspect it is "TDS creep" caused by the on-off of the RO system ...
Everything I've read talks about 95% rejection, so your post TSD should be below 65 (give or take, not sure how accurate these little TDS meters are in real life - though easy enough to mix up a salt solution to test it).

My water is pretty hard, 2x that level must be pretty intense!

RE: 10ppm chlorine 'dosing':

Quote:
I'd worry about how that might affect the RO membrane.
...
Maybe I'm misunderstanding what I thought I read, or not thinking this through, but I would think that a burst of 10 ppm would be OK. Remember, I just place ~ 10 drops in the line, and that's it. So it will pretty quickly get diluted and flushed out the waste port. If the carbon filters can take months of tap chlorine levels, I would think a few minutes of lower levels should be fine. But so far, that burst seems to be enough to keep the bacterial build up at bay - wiping it out before it has time to grow too much.

At any rate, if I do blow out my 16 YO RO membrane, I guess I can spring for a new one!


-ERD50
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