Water pressure drop over house-long run to bathroom

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Gundraw

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I have lived in this house for over a year (built in mid 70's), and one of the most frustrating aspects is the way they ran the water lines to the two bathrooms. Attached is a sketch of the existing plumbing.

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As one can guess from the picture, the main problem is if you are taking a shower in bathroom 2, and someone flushes a toilet in bathroom 1, the water temperature can get downright scary in the shower. Aside from that, none of the pipes are insulated, so getting hot water to either bathroom takes quite a long time. Finally, the installers put the copper pipe against the floor joists with copper bands. When using the hot water, the pipes expanding make it sound like someone is hammering on the floor until they heat up.

My first solution was to buy some insulated 3/4" PEX-a, and do a run from the water heater to the split to each bathroom. Then I would turn both the copper lines into cold water lines. Figured the extra flow on both hot and cold would help the pressure variations, and the PEX would solve the pipe noise problem. I do realize this now makes my time to get hot water even worse.

1654717513610.png


But then I got to thinking: One thing I do have here is pretty high water pressure (80PSI). What if instead I turned one 1/2" copper run into Bath1, the other 1/2" run to bath 2 (alleviating the pressure drop when one bathroom is being used instead of the other). Then run a 1/2" INsulated PEX line for hot water, but put a pressure regulator at the point noted on the sketch.

I know this is a lot of information, but the main questions are this:

1. Is there a better way of solving this problem without putting in a second water heater?
2. Is a water pressure regulator a more effective way of fixing the temperature fluctuation issue than simply bigger plumbing?

I am interested to know how the pros would alleviate these plumbing issues. I have never lived in a home with the bathrooms so far away from the water heater/water supply.

Thanks
 

wwhitney

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And the reason for the temperature fluctuations in the shower is due to the excess pressure drop plus having old shower valves. Modern shower valves are pressure balancing or thermostatic, both of which technologies would reduce temperature variation due to pressure variation.

So in addition to whatever replumbing of water supplies you do, replacing the shower valves is called for.

Cheers, Wayne
 

Reach4

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While 3/4 for each cold would be better, I think 1/2 copper for cold to one bath would be not bad. Just avoid flushing the toilet while somebody is showering in the same bathroom. I am not a pro. So time to get hot water goes way down. You save some water too.

Your pipe runs are pretty long. A hot water recirculation system could be worth considering while you are running new pipes.
 

jadnashua

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The copper institute calls for a maximum velocity of hot water to be 5fps...that equates to only 4gpm with a 1/2" pipe, but 8gpm with a 3/4" one. Just that fact by itself should call for a larger pipe when feeding two bathrooms, especially if it's also feeding other things in the home.

US code calls for NGT 80psi in a residence.
 

Gundraw

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I am appreciating the ideas here. Let me ask a couple more questions:

1. Is there a way to tell if the shower valve is already pressure compensated. I say this, as both bathrooms have updated (albeit 10+ years ago) fixtures. Both bathroom tub/showers have American Standard "Williamsburg" units. Replacing them, due to their locations, would not be trivial.

2. The house is all electric. Perhaps I am going about this the wrong way: Underneath bath 2 (master bath) there is a storage room. Would it be better to convert the long 1/2" lines to cold water and simply put in a second hot water heater? I am just wondering if all this extra plumbing as well as a re-circulation pump may be more of a pain than a second water heater.

3. I did some research on proper sizing for water systems a number of months ago. When I ran all the numbers for the house, I believe it called for a 1 1/4" water meter and 1" water line to the house. My system is plumbed with 3/4" (PVC I believe) for that long 300' run to the meter. Is the long 3/4" run going to be a perpetual problem? I am not planning to tear it out anytime soon, but wondering if I am putting lipstick on a pig. When I called the local water company, they acted like 3/4" was the standard for all these applications.
 

wwhitney

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1) Roughly speaking if it is a one handle control, it should be pressure balanced, and if it has separate hot and cold handles, it is not. However, my experience is limited, particularly on historical units. So maybe post a picture? I suppose it is possible that a pressure balanced valve, faced with an extreme pressure imbalance, will pass significantly hotter water as you describe. I'm not sure if that means it's not working right, or not.

2) The only ongoing downside to a second all electric tank water heater is the additional standby losses, which are fairly low for a well insulated tank without any flue. Plus maintenance. But it may compare favorably with a recirculating system in both those regards. So I would think work considering.

3) Pressure losses add, so even though your 3/4" lateral is undersized, you should size your internal pipes normally or perhaps a little larger (although not on hot, as then you have to wait longer for hot water, absent a recirculating system). And if you have high pressure at the meter, and a PRV at the house, that extra pressure on the lateral will mitigate the undersized lateral somewhat.

Cheers, Wayne
 

jadnashua

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If your install was inspected, depending on which code sequence is used where you live, UPC mandated anti-scald technology in 1997 and IPC followed later in 2000. If it wasn't inspected, could be anything.
 

Jeff H Young

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If your install was inspected, depending on which code sequence is used where you live, UPC mandated anti-scald technology in 1997 and IPC followed later in 2000. If it wasn't inspected, could be anything

mid 70s home
 

Jeff H Young

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whoops I see now that Grundraw says he updated valves so its still possible they are not working properly. I thought original from the 70s
 

Gundraw

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Here is a pic of the Bath 1 tub handles. The shower in Bath 2 is identical except for no diverter valve (shower only).

1654878384555.png


I expect that at some point, the 50 year old 3/4" PVC going to the meter will spring a leak. At that point, I would like to install bigger feed line. Before then, I would love to get the plumbing inside up to snuff.

It should be noted, even if someone just washes their hands in bath 1 (hot water) while taking a shower in bath 2, the shower gets VERY cold but the pressure/flow of the shower does not seem to be interrupted.

@wwhitney - You mention standby losses of a second water heater. I would counter that with the a.) the standby losses in the 70' run of uninsulated copper pipe now (not to mention 3/4" pex after an upgrade). b.) the water losses waiting for hot water to get all the way across the house. Any idea how these losses compare?
 

John Gayewski

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Someone rebuilt old valves, your valves are still the problem. There are ways around that but piping isn't one of them, although it's not impossible to build a balanced system it isn't practical.

Get new shower valves or install a pressure balanced valve if you have access.

A recirc system is way cheaper than another water heater,it's also better for performance. Just insulate what you have and add a recirc line in pex. You won't regret it.
 

wwhitney

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Get new shower valves
Do this. They make horizontal diamond-shaped retrofit plates for exactly this situation. You can remove tile between the two handles and the center to provide a large access for shower valve replacement, and the retrofit plate covers up the hole.

Cheers, Wayne
 

John Gayewski

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Do you mean in up front cost or in operating cost? I could see both of them being a wash, but I haven't run the numbers.

Cheers, Wayne
Both. A pump will likley outlast any water heater (excluding the plastic ones) with little to no maintenence.

Cheaper generally, to me, means how much time and/or money over your lifetime you'll spend on something. This is generally why I'm not a fan of tankless units.
 

jadnashua

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I look at it this way:
- without a recirculation system, you may waste a couple of gallons of water waiting for hot to arrive. You may be paying both for the supply and the sewerage, and unless you go to extremes, it is truly just wasted, not counting the time it takes to finally get hot water when you want it.
- those few gallons are replaced in the tank with incoming cold, meaning less time and volume you'll have hot available
- with a recirculation system, you get to use the entire capacity of the tank, as the lines are hot, so you get a bit more available hot water.
- if you insulate the lines (required by code today on new installations), your standby losses aren't huge especially if you run the recirculation on a timer.

I've had one in my place now for about 20-years. The first one had an internal check valve that finally died, and it was a proprietary design, so I didn't feel it was worthwhile futzing with it as the pump might just have died the next day. I liked that design better than the unit I have, but it works, too.
 

Gundraw

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I did some digging. Both of these fixtures are definitely NOT pressure balanced valves.

Let me summarize all the items so far:

So it sounds like a pressure regulator at the location listed is not a good way of fixing the pressure drop problem.

Would it simply be best to run separate hot and cold lines to each bathroom? I already have two copper lines making the long run, so I could make each of these bathroom specific cold lines (fixes the noise problem), then install two insulated 1/2" pex lines for hot water running to each bathroom, along with a return line for a water recirc system.

The alternative would be combining the two 1/2" copper for cold, and one 3/4" insulated hot. Which is a better solution (particularly with non-pressure balanced fixtures)?

Thanks
 
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