Tankless Water heater

[pjigar]

If your motivation is fewer leaks then I can tell you that the tankless also leaks about the same time. Our tankless leaked after about 8 years which is typical leak period for conventional tank unit in our area.

 

[Ronstar]

Interesting topic!

So, I have a question, how long of wait do you have to wait between showers? If you did laundry how long to recover hot water to shower for example?

I hope this is fine with Ronstar for asking. I'm interested in one too in the near future.

I'm not the best person to answer this, but based on what I'm reading, it's not a time issue between showers, laundry, etc. I believe you can take showers one right after another with no problem, followed by laundry, etc. As long as a single use is followed by another single use.

What is a problem is if multiple showers and laundry are going at the same time. The amount of flow required all at once stretches the limits of the tankless heater.

Again based on what I'm reading but I am no way an expert.

 

[Ronstar]

Another thing to keep in mind, depending on your water chemistry you will need to de scale it regularly. I suspect if your tank heaters are not lasting long you would likely need to descale at least once a year. It's like everything else if you know how to do it, it is not difficult. IF you pay to have it done it will likely cost a couple hundred bucks.. I have two and I just descaled for the first time. If I can do it anyone can..

My research is showing the same thing - says to flush once a year.

If your motivation is fewer leaks then I can tell you that the tankless also leaks about the same time. Our tankless leaked after about 8 years which is typical leak period for conventional tank unit in our area.

I guess I'm ok with a tankless heater having about the same tendency to leak as a tank water heater. But it seems to me that removing/ replacing a tankless
would be a lot less work than removing/ replacing a tank. It's a major ordeal for me to pull a partially filled with sediment tank from the basement and out to the street

 

[Ronstar]

I took my top panel off and it looks like my current tank has a leaking element. Filed a warranty claim and a new element is being mailed and a warranty plumber will put it in. I could do it, but I'll have them do it to preserve the warranty and save me some work.

 

[Texas Proud]

Intersting. I never thought about pressure. We are on a well with a pressure tank, followed by an iron filter. We replaced the iron filer a few years ago and pressure increased.

We have bad water (iron). Neighbor friend only gets about 2 years out his water heaters also.

If you get tank leaks because of your water what makes you think you will not get leaks using a tankless? There are still metal parts to them that I would guess will have the same problem.



What pipes do you have and does the water affect them?


OH.... I did have a tankless on my old house and did not like it... the new ones seem to have taken care of the problem but mine did not heat with low flow... so when I had a water saving shower head it would not come on even with only the hot water on... replacing with a regular head the water was always too hot or no heat at all... One time I had a problem with the system and it overheated the water and it was almost steam coming out of the shower head... very dangerous...


I replaced my water heater a couple of years ago and bought a tank... the cost of tankless was just way too high for any perceived benefit... but this is on a normal house where it should last a long time... BTW, I have only ran out of hot water once in 12 years when we had 3 showers going at the same time... I waited 20 minutes and took a hot shower... the unlimited hot water is good in theory but not really needed...

 

[COcheesehead]

Interesting topic!

So, I have a question, how long of wait do you have to wait between showers? If you did laundry how long to recover hot water to shower for example?

I hope this is fine with Ronstar for asking. I'm interested in one too in the near future.

The hot water is endless. My wife takes 30 minute showers, while we run the washer and I still get hot water at the sink with no surge of any kind in the shower.

 

[Ronstar]

If you get tank leaks because of your water what makes you think you will not get leaks using a tankless? There are still metal parts to them that I would guess will have the same problem.



What pipes do you have and does the water affect them?

My gut feeling is that the conventional tank fills with sediment and /or corrodes over time. And I thought that maybe a tankless would be less apt to do so.

But my main reason for considering tankless is the smaller size when I do need to replace a water heater.

I have cpvc water supply lines, and the water doesn't affect the piping.

We do have an iron filter that precedes the water heater.

 

[mpeirce]

What is a problem is if multiple showers and laundry are going at the same time. The amount of flow required all at once stretches the limits of the tankless heater.

No problem here. We have run three showers at once and there is still hot water in the faucets.

Of course it depends on the size you get.

Properly sized, you shouldn’t have any problems.

 

[ncbill]

I have a dilemma. We have a full time 16000 watt back up generator - not a whole house generator - but one that powers 16 selected circuits during a power outage.

Our 30 amp current tank water heater is wired to our back up generator panel, so that we get hot water during power outages. Under normal conditions, the generator panel is just a sub panel to our main electric panel. During a power outage, the system switches the circuits on the generator panel to natural gas powered generator.

Th back up generator sub panel is fed by a 70 amp breaker from the main panel. The electric tankless water heaters I've researched require 2 and sometimes 3 - 40 amp breakers. A tankless water heater alone would exceed the breaker and wiring capacity of the entire generator sub panel.

So - unless I'm not understanding this correctly, if I got a tankless water heater, I'd have to wire it to the main panel and then not have hot water during power outages.

Or I could go totally crazy and have both tank and tankless. Tankless for everyday use. Then a tanked water heater for power outages.

Stick with an electric tank water heater but switch to an anode-less model.

Those have a liner (our old Vaughn used cement, 200+ lbs. empty!) or a non-metallic tank like the Rheem commercial model linked.

Sounds like your well water remains a problem...add a sediment filter (or maybe a centrifugal sand separator) in addition to the iron treatment.

 

[Time2]

Not sure how it works - I'm just looking at the specs - this one requires 4 -40 amp breakers

I went to the site, they don't explain it, but it does have 4 heating elements, and it says, "Self-modulating power control" which I think means the higher the water flow rate the more heating elements are energized.
The 36kW unit can draw as much as 150 amps. Wow!

 

[Time2]

I got over this issue with a recirculating pump, that has worked great for us. It is an on demand pump. I still have the DW problem though, no matter how much "reminding" I do.

I have a couple of projects to finish, and then I will be doing some plumbing to add a recirculation pump. My bathrooms are 50 ft from the water heater and I don't want to keep reheating water in the much pipe, so I'm only going put the return on the kitchen sink. That is where I want the convenience of instant hot water, to the kitchen. I looked at undersink water heaters, but I don't have wires with enough current capacity to the kitchen.
My plan is to add a return pipe and return the water into the drain at the bottom of the water heater. It's only about 10ft from the heater to the kitchen sink, at least for the return I'll be adding. I'm not sure what length pipe is in the delivery pipe, it seems to take quite a while to get hot water to the kitchen sink located only 9ft away. ¯\_(ツ)_/¯

 

[WhenIsItTime]

My gut feeling is that the conventional tank fills with sediment and /or corrodes over time. And I thought that maybe a tankless would be less apt to do so.

But my main reason for considering tankless is the smaller size when I do need to replace a water heater.

I have cpvc water supply lines, and the water doesn't affect the piping.

We do have an iron filter that precedes the water heater.

Do you ever drain water off the bottom of the water heater? Is it clear or otherwise?

Changing the anode rod every couple years may help.

I have similar situation and investigated options through a couple local dealers. Since I had traditional water heater issues (iron?), I was worried about cleaning tankless yearly and long-term reliability. I ended up going with a Rheem Marathon Electric. It has a plastic tank with fiberglass insulation. Only had it 8 months so far. It is also in a lake house, which we don't use all year so I am not too worried about energy cost.

 

[523HRR]

We have a Navian tankless and love it. It's gas and supplies our heat as well as hot water. Never a problem running everything at once. (2 showers, washing machine etc...)

We also have a Navien tankless (propane). Endless hot water on demand. Also have a separate hot water recirculating line to every tap in the house, so hot water is there in about 2 seconds.

 

[ERD50]

Find out why your/neighbors tanks are only lasting 2~4 years. Never heard of that.

I was on a well, high mineral, fairly high iron. Had a good water softener (one that could handle the ~ 2 ppm (5ppm? I forget) iron w/o a separate filter. Tanks was still going just fine 30 years later (just had it replaced when the HVAC was replaced).

As mentioned, verify pressure doesn't ever go much above 60 PSI (just because you saw 55 doesn't mean it stays there). Is there some water-hammering? Is your pressure tank providing a cushion, or do you need an expansion tank? Might be a check valve somewhere preventing pressure release? pH? Sounds like you need a sediment filter.

Whatever water problems you have might effect the tankless as well.

-ERD50

 

[Texas Proud]

We also have a Navien tankless (propane). Endless hot water on demand. Also have a separate hot water recirculating line to every tap in the house, so hot water is there in about 2 seconds.

Just curious how you get recirculation on a tankless... to me that would mean it was on all the time... sounds like a waste...


With a tank you are moving hot water from the tank to your faucets and back to the tank with hot water... you only have to replace the heat lost on the round trip...

 

[mpeirce]

Just curious how you get recirculation on a tankless... to me that would mean it was on all the time... sounds like a waste...

With a tank you are moving hot water from the tank to your faucets and back to the tank with hot water... you only have to replace the heat lost on the round trip...

Same with a tankless. The hot water in the hot water pipes is circulating. The tankless is the same. If the water temp falls below a certain level, the heater fires up briefly.

We have the recirc pump turn off at night. Also, the recirc lines are insulated, so heat loss isn’t all that much. Also, when we leave the house the system turns off the recirc pump automatically and it turns back on when we return. Also off when travel.


As I said, instant hot water via a recirc pump is a BTD item - with or without a tank. You’d never do it is you are trying to eke out savings on your hot water bill.

We have the tankless for the endless supply of hot water. We have the recirc pump so there’s hot water at each tap. We love it (esp. DW).

 

[FLSUnFIRE]

Had one, wouldn't want one again -one too many cold showers due to faults shutting it down, when it draws power it draws so the energy savings are mythical IMO. I'll consider a heat pump model when I replace (especially if I could duct the cool air into the house) but for now have a conventional tank and time based electricity billing and have it on a timer to "charge" in the middle of the night when electricity is cheaper.

 

[COcheesehead]

Just curious how you get recirculation on a tankless... to me that would mean it was on all the time... sounds like a waste...


With a tank you are moving hot water from the tank to your faucets and back to the tank with hot water... you only have to replace the heat lost on the round trip...

It recirculates based on how you have it programmed. There is a comfort setting which recirculates about every hour and there is an economy setting that recirculates about half that. There is also an app for scheduling it to your lifestyle. We shut it down completely from 10pm to 5am to save energy.

 

[Texas Proud]

Same with a tankless. The hot water in the hot water pipes is circulating. The tankless is the same. If the water temp falls below a certain level, the heater fires up briefly.

We have the recirc pump turn off at night. Also, the recirc lines are insulated, so heat loss isn’t all that much. Also, when we leave the house the system turns off the recirc pump automatically and it turns back on when we return. Also off when travel.


As I said, instant hot water via a recirc pump is a BTD item - with or without a tank. You’d never do it is you are trying to eke out savings on your hot water bill.

We have the tankless for the endless supply of hot water. We have the recirc pump so there’s hot water at each tap. We love it (esp. DW).

So basically you are saying that your pipes are the 'tank'...



Do you have a manifold that goes to each faucet? I am wondering how it is able to get to all faucets... you need a line to and from each faucet in my thinking so there has to be a common point for the pump...

 

[mpeirce]

I'll consider a heat pump model when I replace (especially if I could duct the cool air into the house)

Yeah, that’s a whole other kettle of fish.

I looked into those when we did the big renovation.

Issues include a pretty lengthy recharge time when you run out of hot water. The heat pump is more efficient, but slower than burning gas or using electric heating elements.

And like you said about the cool air. It produces cool air as an output (since it’s pumping the heat out of some air into the water). This can be nice in the summer, but if you have cold weather, it’s rather counter productive during that time of year.

It also need a fairly large air area to draw from so it can’t be jammed into a tight closet with little ventilation.

They typically are more expensive as well, so even though they save heating costs, the up front costs can be steep.

So another option to evaluate in the mix...

 

[Dash man]

We have four Navien tankless gas water heaters in four different properties. They work great and we haven’t had any problems in the six years since we installed them.

 

[eytonxav]

We have had a Rinnai going on 10 years and it is great. One unit for the whole house. Get all the hot water we need and I would say it's energy efficient being a gas fired unit. Maintenance wise, we do a descaling treatment every couple of years, but that is it.

 

[street]

cocheesehead and Ronstar, thanks for clarifying.

 

[Happyras]

Thanks for your post, you inspired me to descale our Rinnai gas fired. It will be the first time in 12 years or so, so I had to buy a few fittings. Anyway, these are great if gas, a poor choice for electric unless you have lots of space in a 400 amp service. I replaced a gas tank some 12 years ago. I cross connected to another electric tank (since replaced with a smaller size) and put in a recirc pump on that tank with Alexa controlled ball valves and pump with thermal switches. Yup, I an enginurd by degree. These type of systems are fun and much easier than the industrial distributed controlled systems I installed, in my career. For the OP, I think a little water treatment ahead of a conventional tank heater is the way to go. I was a senior PM for a major water systems company and that is my humble opinion......

 

[Time2]

So basically you are saying that your pipes are the 'tank'...

Ya, it is kinda like that, the heated water is in the pipes ready to flow out of the faucet. If it cools to a certain temperature the pump will circulate it until the water at the faucet is brought back up to temperature. The recirculating pumps I am familiar with, have a temperature operated Valve that is connected at the faucet, between the hot water line and the cold water line. When the pump is running and the value has opened because the temperature dropped below 90*F, the water in the hot water line is pumped (circulated) into the cold water line, this continues until the water going through the valve gets to 90*F and the valve shuts. The water in the cold water pipe is warmer than it would be without the recirculation system. The pump is often on a timer, so it runs every other 15 minutes and off at night. You can have a separate pipe for the return rather then using the cold water pipe.
I have some electro-mechanical abilities, after I get a a couple of other projects finished, I have a plan to build a temperature operated pump. I''ll have a temperature sensor at the hot water faucet connected to a circuit that will turn on the pump when the temp drops to 100* and shuts of when the temperature reaches 120*F. I'll also return the cooled water to the bottom of the water heater.

Do you have a manifold that goes to each faucet? I am wondering how it is able to get to all faucets... you need a line to and from each faucet in my thinking so there has to be a common point for the pump...

In my home, I'm pretty sure the pipe runs from the water heater the length of the house and has a T at the kitchen and another T at both bathrooms. The pump is installed on top of the water heater and pumps the heated water the length of the house. The temperature operated valve can be located at the farthest faucet, this will keep hot water close to all faucets.