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Shower 1/2" to 3/4" Water Supply Question.
Old 10-05-2010, 08:41 AM   #1
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Shower 1/2" to 3/4" Water Supply Question.

It's possible I may be able to get a great deal on a whole 3/4" Thermostatic+Bodyspry set up for a great price but I have 1/2" supply lines. The water pressure is 65 psi and the set up diagrams senerio's are listed below. I was wondering if there would be a problem if I went from 1/2" to 3/4" on the supply lines right before I went into the thermostic valve and remained 3/4" since each conection is 3/4". Would the loss in volume be a problem?

Info on the unit is 3/4" Thermostatic rough-in casting with plug. Supports 12GPM at 80PSI, 3/4" NPT inlets and Outlets. 3/4" Volume Control Valve, Allows 4 Independent volume control per outlet, on/off functionality, 3/4"- NPT Inlets and Outlets.

Diagram #4 are the items in the package but if volume would be a problem I could always go with #3 and add a volume control.


If I don't have enough water pressure or volume, will it work with two less body wash heads and a diverter valve instead?
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Old 10-05-2010, 09:18 AM   #2
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General unsolicited comment: AL Gore is NOT going to like this. Seriously, does anyone really need a shower that consumes 12 GPM? Now, if you had a whole rugby team crowded into your shower, I could understand it, but really . . .

Technical:
- Will your present 1/2" provide 12 GPM at the shower? At 65 PSI I wouldn't think this would be a problem, but lots could depend on pressure losses/flow restrictions that occur upstream (valves, lots of small-radius elbows, scale buildup inside the pipe, etc).

- The real issue isn't the 3/4" lines used in the unit. You could go to 2" pipes inside the showerhead plumbing and the fundamental question would still boil down to the flow rate at the showerheads, right?

- This might be a good question for the Price-Pfister tech folks, if you want to be sure.
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Old 10-05-2010, 11:14 AM   #3
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it's not a question of pressure, IIRC, as pipes in "parallel" preserve their pressure, but split the flow rate. I would be less concerned with the pressure and more concerned with the volumetric rate (as samclem points out). since, no data about rate was given, it's very difficult to say.
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Old 10-05-2010, 11:18 AM   #4
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Do you have a conventional shower head there now? If so, I think that you could take off the shower head and just fill a bucket off the open 1/2" pipe sticking off the wall. Time how long it takes to deliver a gallon or five gallons.

Ditto what samclem said about usage. 12 GPM is a Hummer of a shower.
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Old 10-05-2010, 11:56 AM   #5
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Two other issues to consider:
- Hot water supplies. While a typical tank-type unit might hold 40-80 gallons, the water coming out of them won't be sufficiently warm for a comfortable shower if you rapidly use half of that amount, especially if incoming water temps are cool. Tankless natural gas water heaters usually produce 2-5 GPM depending on the temp of the incoming water, though you can find bigger units.
- Drain capacity: I know the tub/shower drain in our house wouldn't be able to handle the flow rates we're talking about here. I'm sure more modern homes have higher capacity drains, but you'd want to check on yours. If you do as travelover suggests to monitor the max GPM of your supply line though the showerhead connection, you might want to let that baby run full bore for about 5-10 minutes to see if the water backs up in the shower pan. Also, be aware that, depending on the restrictions in your present shower valves, those 1/2" lines leading to your shower might be capable of supplying more water than will flow to your present showerhead connection (and be collected in this test).

Suggested additional steps to make amends for the environmental impact of this installation.
- Sell all motorized vehicles and resort to bicycle transportation.
- Eschew heat and AC for your home 9 months of the year
- Recycle all of your children
- Collect and store all rainwater from your home's roof, as well as the roof of at least one Walmart, to feed this thing.
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Old 10-05-2010, 01:17 PM   #6
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Quote:
Originally Posted by samclem View Post
Seriously, does anyone really need a shower that consumes 12 GPM?
It states its "capable" of 12 gpm at 80 psi. My pressure is only 65 psi and no I won't be using anywhere near that amount.

Quote:
Originally Posted by samclem View Post
At 65 PSI I wouldn't think this would be a problem, but lots could depend on pressure losses/flow restrictions that occur upstream (valves, lots of small-radius elbows, scale buildup inside the pipe, etc).
I could eliminate say 4 bends which would help the flow rate.......yes?
Quote:
Originally Posted by samclem View Post
- This might be a good question for the Price-Pfister tech folks, if you want to be sure.
I've sent them a detailed email of which I've received no response. I would imagine the standard response would be, "why didn't you just purchase the 1/2" thermostatic valve instead", not wanting to let them know of the amazing deal I can get on a 3/4" system.
Quote:
Originally Posted by travelover View Post
I think that you could take off the shower head and just fill a bucket off the open 1/2" pipe sticking off the wall. Time how long it takes to deliver a gallon or five gallons.
If I got the flow rate, combined with the 65 psi I presently know, will this help determine whether this system will be compatible?
Quote:
Originally Posted by samclem View Post
While a typical tank-type unit might hold 40-80 gallons, the water coming out of them won't be sufficiently warm for a comfortable shower if you rapidly use half of that amount, especially if incoming water temps are cool.
Quote:
Originally Posted by samclem View Post
- Drain capacity: you'd want to check on yours. If you do as travelover suggests to monitor the max GPM of your supply line though the showerhead connection, you might want to let that baby run full bore for about 5-10 minutes to see if the water backs up in the shower pan. Also, be aware that, depending on the restrictions in your present shower valves, those 1/2" lines leading to your shower might be capable of supplying more water than will flow to your present showerhead connection (and be collected in this test).
Let me recap, I won't be getting 12 gpm since I don't have 80 psi pressure.
I will work on getting the flow rate although that will all change once a new system is installed.
What if I eliminated 4 90 degree bends, I would assume that would help with flow rate.
I won't be using all heads at once therefore drain flow or gpm won't be as important.
I'm thinking rather then 3 volume control valve I would use only two and a diverter valve therefore only two systems could be used at once.

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Old 10-05-2010, 02:40 PM   #7
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Also, do you really want those body spray heads? We got them in the master bathroom when we built our house, and have turned them on exactly one time. They add absolutely nothing to the experience, and waste water and pressure. A perfect example of "anything worth doing is worth overdoing". A total waste, IMHO.
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Old 10-05-2010, 03:39 PM   #8
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Quote:
Originally Posted by My Dream View Post
Let me recap, I won't be getting 12 gpm since I don't have 80 psi pressure.
What if I eliminated 4 90 degree bends, I would assume that would help with flow rate.
I won't be using all heads at once therefore drain flow or gpm won't be as important.I'm thinking rather then 3 volume control valve I would use only two and a diverter valve therefore only two systems could be used at once.
Well, your poster name is "My Dream".

Pressure is proportional to the square of the flow rate, so if you reduce the pressure from 80 PSI to 65 PSI you'll still have 90% of the flow-- over 10 GPM. I think that's the difference between standing under a waterfall and standing outside during a torrential downpour, but either way it's still more rinse water than you'll ever need.

Eliminating 90-degree bends doesn't help as much as you'd think. It does reduce piping resistance a tad but I'm not sure that you'd see a significant change in flow. Nukes add all sorts of piping bends to their reactor plants to help with thermal expansion and hydraulic shock because the bends offer significant advantages without significantly reducing flow. Of course there are other problems with crud getting stuck in the piping bends, but you're not likely to have to deal with this issue.

Before you whip out your credit card, have you tried an Oxygenics shower head? Spouse stumbled across one of these in a Miami hotel and was so impressed that we replaced the nozzles in both our bathrooms and our rental home's showers. 65 PSI will easily give you 2 GPM that strips off our Hawaii red dirt (and probably a layer or two of skin) and will give you more than enough spray over whatever part of your body you're trying to reach. Best of all, the shower head never needs cleaning or demineralizing. It's been at least two years in our showers and it looks brand-new.

Considering the money you may be contemplating spending, an Oxygenics is a cheap experiment... and if you decide to go with your shower from hell then you'd probably get over half your Oxygenics money back by selling it on Craigslist.
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Old 10-05-2010, 03:54 PM   #9
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Hope you have a gas water heater with a very large tank. You may even need to set it at an very high temperature (150+) and add a thermostatic mixing valve at the tank to drop the supply temperature to 120. (Disclaimer: I am not a plumber.)
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Old 10-05-2010, 06:19 PM   #10
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Hope you have a gas water heater with a very large tank. You may even need to set it at an very high temperature (150+) and add a thermostatic mixing valve at the tank to drop the supply temperature to 120. (Disclaimer: I am not a plumber.)
I didn't even think about the size of the water heater. It'd suck to only have an eight-minute shower under those 10 GPM conditions... I guess you could do it as a couple of 30-second submarine-shower bursts but that sort of invalidates the whole point of the upgrade.
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Old 10-05-2010, 09:19 PM   #11
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It states its "capable" of 12 gpm at 80 psi. My pressure is only 65 psi and no I won't be using anywhere near that amount.
As Nords said, the pressure difference won't make that much difference in flow.

But you haven't told us - how many GPM do you expect to actually use? That is what is key - not what it is 'capable of' (which could mean all sorts of things). I have an extension cord 'capable of' handling 20 Amps - but if I plug in a night light, it uses ~ 1/20 Amp. I could plug a light-weight extension cord in between w/o problems. That's equivalent to your 1/2" supply lines feeding a 3/4" device. It depends on the actual draw.

What I'm saying is - you haven't defined the problem properly. And if you are going to use even 10 GPM, then all the other posts about supply, drain capability, new water heater, etc must be considered. How much is this great deal going to cost you?

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Old 10-06-2010, 08:13 AM   #12
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Also, do you really want those body spray heads?
What got me to want this change was having a shower at a resort which had this set up and both my wife and I really enjoyed the experience. I wouldn't spend the extra money if I wasn't sure I would enjoy the outcome.
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Pressure is proportional to the square of the flow rate, so if you reduce the pressure from 80 PSI to 65 PSI you'll still have 90% of the flow-- over 10 GPM. Either way it's still more rinse water than you'll ever need.
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Eliminating 90-degree bends doesn't help as much as you'd think. It does reduce piping resistance a tad but I'm not sure that you'd see a significant change in flow. Before you whip out your credit card, have you tried an Oxygenics shower head?
Considering the money you may be contemplating spending, an Oxygenics is a cheap experiment... and if you decide to go with your shower from hell then you'd probably get over half your Oxygenics money back by selling it on Craigslist.
It sounds as though pressure isn't my problem then, and I'm still not sure of flow rate. As for the Oxygenics shower head, no I haven't tried them and I would like to one day but it still doesn't help in the way of a thermostatic valve which I'm really interested in. The shower head and valve serve two different purposes. Also I like the experience of having the body wash positioned lower then the shower head and having it directed straight forward as well as separate adjustments for each individual spray. To me it's sort of comparing apples to oranges but I don't want to debate this, especially with you Nords since......well let's leave it at that.
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Hope you have a gas water heater with a very large tank. You may even need to set it at a very high temperature (150+) and add a thermostatic mixing valve at the tank to drop the supply temperature to 120. (Disclaimer: I am not a plumber.)
I replaced the natural gas water heater couple years ago and upgraded the size. Setting it at 150 doesn't make sense due to other faucets etc. in the home.
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But you haven't told us - how many GPM do you expect to actually use? That is what is key - not what it is 'capable of' (which could mean all sorts of things). I have an extension cord 'capable of' handling 20 Amps - but if I plug in a night light, it uses ~ 1/20 Amp. I could plug a light-weight extension cord in between w/o problems. That's equivalent to your 1/2" supply lines feeding a 3/4" device. It depends on the actual draw.
I had no idea that going from 1/2" to 3/4" made that much of a difference as your example of 1/20 of an amp described, I learned something new. I may just use a diverter instead of volume control to reduce the amount of heads in use and better control the water flow rate. I've also left the water flow at maximum for 10 minutes and the drain had no problems with the flow.

Oh and no I still haven't determined the flow rate yet but do appreciate the responses so far.
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Old 10-06-2010, 01:44 PM   #13
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To me it's sort of comparing apples to oranges but I don't want to debate this, especially with you Nords since......well let's leave it at that.
It's not whether we agree or disagree but whether all the issues have been covered. Sometimes the dialogue brings out points that neither side appreciated in the first few posts.

I've been bitten many many times by expensive decisions that lacked engineering quality but tried to make up for it with décor & features.

If you liked what the resort offered then you should literally go out and buy what the resort has. Call up their facilities manager, ask him how well it's working out for repairs and maintenance, and figure out where to buy one for yourself. (That's what we did with the Oxygenics.) Buying from Disney will avoid a lot of time, hassle, and potential disappointment of trying to recreate Disneyland in your bathroom.

Of course it's not as much fun as trying to design from scratch over the Internet with people who are wondering what they'll do all day...
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Old 10-06-2010, 01:59 PM   #14
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I had no idea that going from 1/2" to 3/4" made that much of a difference as your example of 1/20 of an amp described, I learned something new.
"Equivalent" was probably not the right word for me to use, "Illustrative" would have been better - I didn't mean that the 1/2" to 3/4" plumbing would have a 20x factor on flow. What I meant was you can't determine anything at all until you know what your flow rate is. It might be major issue, or it might be a non-issue.

With a night lite, a circuit that can only supply 1/20th of an amp (small wires, small fuse - analogous to small plumbing lines) would be a non-issue.

If I try to plug a large draw device (hair-dryer, toaster, Micro-Wave, etc), that 1/20th amp circuit just won't do it. I'll blow the fuse or start the wires on fire. Nothing so dramatic with plumbing, but if your supply can't handle the flow that you use, you might just get a trickle from each of those shower heads - depending on how low the flow supply versus what you use is.

-ERD50
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Old 10-07-2010, 10:17 AM   #15
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If you liked what the resort offered then you should literally go out and buy what the resort has. Call up their facilities manager, ask him how well it's working out for repairs and maintenance, and figure out where to buy one for yourself.
It was a high end resort so I doubt we'll ever be back to the same one again. they also had different hot water tanks, size of piping, pressure, flow rate, etc. therefore there were too many variables outside of the actual brand and model number of the actual Shower Faucet system, but I got your point.

Quote:
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If I try to plug a large draw device (hair-dryer, toaster, Micro-Wave, etc), that 1/20th amp circuit just won't do it. I'll blow the fuse or start the wires on fire. Nothing so dramatic with plumbing, but if your supply can't handle the flow that you use, you might just get a trickle from each of those shower heads - depending on how low the flow supply versus what you use is.
I got the just of what you were trying to say but didn't want to be sarcastic in my reply. I somewhat understand the difference between the 1/2' to 3/4" run and know enough about electricity to understand amps/wattage draw etc. Yes maybe a little ........ but I got the message.

In conclusion it was my neighbour who says he determined the 65 psi water supply with a gauge he borrowed last year. Yesterday I got my own gauge and tested the outdoor water faucet and it came in at 78 psi. Borrowed another gauge and got the same reading therefore the pressure is much greater then I thought at first. I haven't had the time to check flow rate yet but as it stands now, the 80% off deal that I was able to get has since been sold to someone else. He did mention if another one came up he'd let me know.

In the mean time I'll try to get the flow rate but it would appear that our house water pressure is "A OK!".

Thanks
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Old 10-08-2010, 04:14 PM   #16
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From a similar question/answer on GardenWeb....regarding a 10gpm shower unit....the answer from someone who appeared to know how to design piping was:

Consulting the "Type L Copper Friction Loss Table" we find that if we supply this shower with a 1/2" line the velocity of flow would be 13.80ft/sec and the pressure loss would be 67.72psi/100ft of pipe. If we increase the pipe size to 3/4" the velocity of flow is 6.62ft/sec and a pressure loss of 11.17psi/100ft.

He previously stated that velocities in excess of 8 ft/sec cause excess erosion of copper pipes, so the combination of 13.8 ft/sec velocity and 67 psi/100ft pressure drop suggest to me that 1/2" service to your dream shower isn't going to work very well or long when you open all the valves.
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Old 10-12-2010, 06:53 AM   #17
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Thanks for the information scrinch, I'm actually surprised at the "pressure loss would be 67.72psi/100ft of pipe" results.
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Old 11-19-2010, 07:51 AM   #18
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Well folks, I bit the bullet and bought it, (shipping to the US) and will be picking it up in about 3 weeks. Nope they don't ship to Canada and I should start redoing the bathroom in about 6 weeks since I need to purchase the rest of the items. I won't start till I have everything.

I hope to let you know the end result once finished.

Thanks for everyone's help.
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