Water Pressure Question/Problem?

My in-house water supply pressure is set to 50 psi with a PRV. Whenever any faucet is opened the pressure drops to about 40 psi and stays there until the faucet is closed. All my pipes are copper with ¾†pipe coming from the PRV and ½†pipes branching off this pipe to individual faucets. Is this pressure drop normal or do I have a problem with my PRV or something else for that matter? The issue for me is not simply the fact that there is a pressure drop but that it is difficult to take a shower if anyone turns on another faucet in the house. This is especially prominent if a hot water faucet is turned on while taking a shower. We then experience for lack of a better word - “hot water starvation†in the shower. If two faucets are open at the same time the pressure drops even further to about 35 psi. By the way I have a 50 gallon Rheem hot water heater. I appreciate any advice as to how/if this problem can be alleviated.

Thank you,

Jerry

To find the problem, you need to know the pressure at various places in the system. If you can put pressure gauges at a few places you can find out where the losses are. Without pressure measurements at known locations, all you can get here is wild speculation.

It is probably more than you want, but ideally, I would want pressure gauges at:
1. Inlet to PRV (low priority unless you find a problem at outlet of PRV)
2. Outlet of PRV
3. Inlet of hot water heater (low priority)
4. Outlet of hot water heater (low priority)
5. Outlet of tempering valve
6. Somewhere near the problem shower

If you have multiple gauges, record the pressure reading when there is no flow. They can differ by 3 to 5 psi and that is significant if you are trying to diagnose pressure drops.

If you have all individual fixtures on 1/2" copper pipe running off 3/4" pipe you should have plenty of pipe unless you have very high flow devices such as some super-shower, or 80 ft of 1/2" pipe to the shower. You will never completely avoid reduction of flow when another faucet or shower is turned on. The best way to reduce the effect is with a temperature controlled shower faucet. You can get some benefit by increasing the system pressure.

The first place I would check is at the PRV inlet and discharge. If the pressure is dropping a lot there, then you have the location of one of the problems. Is the inlet pressure high enough? Is the PRV big enough? If the inlet isn't at least 10 PSI greater than the desired outlet pressure, then it may not be able to deliver the pressure you have it set at. Does the inlet pressure drop when you run water; or just the outlet pressure? If the inlet pressure drops, you have a problem with the inlet piping or the valve.

There is often a strainer in the PRV, probably under something like a plug or a cap on the inlet side. Turn off your main supply valve and take a look at the strainer; clean if necessary.

Then, I suggest that you increase the PRV setting to about 65 PSI.

Do you have any kind of filter? If you do, you should have pressure gauges at the inlet and outlet. If you have a filter after the PRV, the filter pressure drop will affect the pressure available to users. It's better to have the filter before the PRV in a municipal supply system so you get constant pressure even when the filter starts to plug; but most people don't do it that way. If you have a municipal supply, I suggest you take the cartridge out and see if it improves performance.

You can get a lot of hot-water pressure drop at a tempering valve if you have one. They are often little dinky things that don't have the capacity for multiple hot water uses. You would get a little benefit if you increase the setting on the tempering valve, and on the hot water heater, but you increase the risk of scalding. It is especially a problem if your water supply is colder in the winter because you get less flow supplement from the cold water. If you measure the pressure after the hot water heater and after the tempering valve you will know if that is contributing to the problem.

How old is your home? If you have a galv. pipe coming in you may have enough restriction,due to rust, to cause the gauge to drop to 40 while water is running and come back up when you close a valve.

If everything is copper and the service pipe is plastic or copper it is most likely the PRV. Try adjusting the PRV for more pressure.

If you have an old main shutoff with a washer, it (the washer) may have come loose and is not allowing the water to flow right,but this is not likely.

Bob - Thank you very much for all the information. I don't have any high flow devices, filters, or a tempering valve. Looks like I do have a lot of work ahead of me in trying to pin down these problem. I'll start by taking pressure readings at the inlet and oulet of the PRV and proceed from there.

Cass - I appreciate your input. The house was built in 1928 but the plumbing has been updated. The service pipe coming into the house is copper. Just for my education, besides contamination and/or rust, what can go wrong with a PRV to cause a problem like this?

I'll increase the PRV setting to 65 psi. When the PRV was installed it was set to 40 psi. I've read somewhere that it should be between 40 psi - 60 psi so I chose the midpoint, 50 psi, in the hopes of alleviating this problem. Obviously it wasn't enough. What is the maximum safe setting for in-house water pressure?

Thank you again,

Jerry

2 other things, some PRVs have a screen that can plug so you may want to check that also if the city is working on the line or there is a break your service pressure may be lower then the PRV setting. I had a customer that had to live with 30# max. for months. 55-65# is good pressure.

My PRV is a Watts U5B. It appears that this valve has an integral strainer. Do I have to remove the PRV to service the strainer or can that be done on site?

Turn off the water and unscrew it at the union and you should see it.

I couldn't find the U5B to locate the strainer port, but if there is a strainer there is usually a hex head plug that can be unscrewed after you turn off the supply pressure to the valve.

What is the size of the valve; the pipe size in and out? If it is too small it will not be able to pass the required flow. You should have at least a 3/4" regulator.

If the inlet pressure is in an acceptable range and the regulator is the problem, you could eliminate the regulator by taking the internal parts out of it.

If you need to buy a new one, the 3/4" Watts N35-BU-3/4 is $43.90 and the N35-BU 1" is $61.85 at Grainger.

The pipe size in and out of the PRV is 3/4". I don't know as yet what the inlet pressure is but I do have an outdoor faucet that comes off the inlet pipe so I can check the pressure there as soon as I get a gauge. However if I had to guess just by watching the water come out of that faucet I would say it was "high". It's certainly gushes out with a much larger force then anything inside the house.

I checked the inlet pressure and it is 116 psi. With one faucet inside the house fully open, the inlet pressure drops a bit to 112 psi. Inside the house, with the water pressure set at 50 psi by the PRV and the same faucet open, the pressure drops to 40 psi. The pressure gauge utilized to measure water pressure inside the house is located at the inlet to the water heater. It comes off a 3/4" pipe which in turn branches off a 3/4" main supply line. I venture to say that if I am dropping 10 psi at this location perhaps the drop is even higher further down where the 3/4" supply line branches off to various sink faucets and shower via 1/2" pipes. I did check the PRV strainer and it was clean. Are there any other tests that I can perform to see if it's the PRV before replacing it. I would hate to spend the time and money in doing that just to find out that I've gained nothing.

Thank you,

Jerry

That is dropping a lot of pressure at the regulator. It is running almost closed and that means there is very little control range. I would start by setting the regulator at 65 psi.

There is usually a lock nut at the top of the bonnet which should be loosened; then the screw at the top tightened to increase the pressure setting. Then tighten the lock nut.

You can repair the regulators if they have bad parts but I wouldn't count on it solving the problem. Check the price at a plumbing supply for a new kit. A new one from Grainger is reasonably priced and you have time to get it. It may be cheaper than the repair kit.

You might try closing down the valve at the inlet of the regulator if you have one (not the main stop at the street). The effect of that would be to decrease the inlet pressure when you have high flow, and it would let the PRV operate more open. It might have better control range.

I would adjust it by opening a couple of valves or faucets in the house, and then throttle the inlet to the regulator until it is reading about 85 psi with the regulator set at 65 psi. See if that helps enough to make it satisfactory.

first thing I would do is throw that Watts piece of crap into the garbage! Everything that watts makes is crap! Go out and buy a Cash Acme reducing valve and make sure it is of all bronze construction! No IRON! I didn't look up the the specs of your existing one but I'll bet it's iron bodied, almost all there stuff is! When the watts feed valve blew in my house i took it apart and not only were all internal pasageways restrited but the sediment screen was also rotted out too.
I don't think you have any problems with constrictions/clogging in any of your plumbing since your not stating that when any single faucet is turned on that there is any flow problems, only when multiple taps are opened. put a bucket under any of these outlets and see how long it takes to fill and figure out thier respective gpm. All fittings that are IAPMO approved are rated at 45 psi and have to maintian that flow to 80psi. your figures shouldn't vary being set at 50psi.
Remember this tho as long as the system is closed anywhere you test whether is a 4" pipe or a 1/2" pipe your pressure will remain constant if the system is closed. Pipe size only varies flow rate.
As far as your shower goes and not having enuf hot water? what is the recovery rate of this rheem unit? are you trying to get 13gpm out of say a Grohe shower body while only feeding it with a HW Heater that has a 30gph recovery rate? and what is the tempature rise of the water that you are heating? if your looking to run a big shower head or mult body sprays and you have a 100 degree temp differential, your only gonna get about 5 minutes of HW if that much!
Unfortunatly your water pressure will always drop when you open any faucet, the actual pressure that is coming out of the faucet is less than 5lbs. if I remember correctly a 3/4" line unrestricted @ 45psi should flow something like 33gpm and if the PRV is rated lower than that go to larger size that does.
now your inlet pressure is 116 ils outlet set at 50, a 66 lb differential on its best day that watts prv only gave you about 11gpm thru it. bump it up to 65 lbs maybe ya'll see another 2gpm.

I checked the flow rate at a basement faucet where the water discharge seems good and it was 8 gpm. For comparison I also checked it at the outside faucet where the water pressure is 116 psi and the flow rate there was about 13 gpm. I have not had a chance as yet to increase the indoor pressure to 65 psi but that is coming up next. I don't think the PRV is corroded. I checked the strainer and it was clean. As far as lack of hot water goes maybe I didn’t state that clearly. There is enough hot water. It’s just that the flow drops considerably if another faucet is open while someone is taking a shower. If that faucet is closed, everything is back to normal. I should add that the showerhead is standard. It's not oversize and there are no body spray additions in the shower. I did find the specs for the PRV, and they are as follows:

MATERIALS

Bronze body construction
Renewable stainless steel seat
Renewable stainless steel integral strainer screen
Reinforced Nordel diaphragm ½" - 1" (15-25mm)
Reinforced Buna ‘N’ diaphragm 1 ¼" - 2" (32-50mm)
Buna ‘N’ valve disc

PRESSURE-TEMPERATURE

U5B ½"-2" (15-50mm)
Suitable for initial pressures up to 300 psi (21 bars).
Reduced pressure range 25-75 psi (1.72-5.17 bars).
Set for 50 psi (3.5 bars) no flow pressure unless otherwise specified.
Operating temperatures up to 160°F (71°C).

Have you tried putting flow restrictors in all faucets in your house? If all lav faucets are giving you a flow rate of 8gpm then thats way too much water at each sink. Restrict each faucet in your house with aerators that are rated @ 2.2-2.5gpm @80psi.You don't need more water than that. What your experiencing are normal occurances when multiple things are being turned on. Water is going to flow to where it has least resistance.
Turn on your washing machine doing a WW wash.....you won't be able to take a shower.same thing is going to happen if you turn on garden hose outside also.
I'm guessing that this is a single family house with boiler HW heater washingmachine PRV in basement and shower on the uppermost floor? If so, if there was a shower in the basement the opposite would happen. while you were showering nobody else would be able to use any HW in the house. I don't think that by increasing the pressure to 65lbs that you will see any difference. any increase you will see will also be shared by anyone else who would also open up a faucet while you were showering.
probably the only way for you to enjoy an unmolested shower would be to repipe your shower and adding its own HW heater(in attic above or closet nearby)and supplying that with its own dedicated water supply right from the PRV.

Thank you for your advice. I only have one faucet inside the house without a flow restrictor and this is the faucet that I tested for flow rate - 8 gpm. The other faucets do have flow restrictors and obviously a reduced flow rate. But even opening these faucets impacts the upstairs shower. Your guess about the house layout is very accurate. The water heater is a Rheem 50 gallon natural gas unit. It's about 1 year old. I do have another shower in the basement and there is more water flow in this shower but I have to add that the showerhead downstairs is of a European make, and does not have a flow restrictor. The impact in this shower of turning on another faucet is not as pronounced as upstairs, but is still not all that comfortable. I can live with the situation but just wanted to know if this is typical or whether I have a problem that can be easily remedied. It seems that there is no easy solution. I will still try to jack up the house pressure to 65 psi just to experiment and for my personal education. Interestingly when I was looking for information about PRVs (Watts, Cash Acme), the recommended water pressure for household use in the PRV literature was 50 psi, which is my current setting. Also I found it interesting that the installation instructions for a Watts PRV state that it can be installed vertically or horizontally (mine is a vertical installation), whereas for Cash Acme PRV only a horizontal installation is recommended.