How to reduce water pressure

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Old 01-25-11, 11:53 AM
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How to reduce water pressure

I have strong evidence that the water pressure in our new house is very high- high water velocity at the facets, noticeable flow noise when using fixtures, not only the washer but even the toiler sometimes makes baning noise when it stops filling up the tank.

I know I can install the pressure reducing valve to address this issue but I was thinking of two other possibly more attractive alternatives.

1) wouldn't simply closing the main shut off valve some amount reduce the pressure?
2) I was thinking of installing whole house filtering system for other reasons. Wouldn't it also reduce the pressure?

Thanks for your comments in advance.
 
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Old 01-25-11, 12:16 PM
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Closing the main partially will only reduce the flow when things are in use. Pressure will still rise when faucets are closed.

Pretty much the same with the filter.

You need a PRV (and probably an expansion tank on the water heater).....

Pressure gauges are about $10 most anywhere...need to do some checking..
 
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Old 01-25-11, 06:04 PM
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I'm getting the gauge soon and will have the exact number but I talked the town water guy and he said that in our block (it's on a moderate slope) low point is 110psi and the top is about 70psi. We are more on the top of the slope so I'm expecting at least 70+psi.

Come to think about it, you are right that they won't lower the pressure but the flow. But than, isn't that what I want in terms of preventing water hammer? Water hammer is caused by high velocity of the water right? In general the high velocity is due to the high pressure in the system but if your flow rate is decreased, that will decrease the water hammer, wouldn't it.
 
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Old 01-25-11, 08:00 PM
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What about adding air chambers (air cushions) to absorb the shock wave. They are an inexpensive and common fix.
 
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Old 01-25-11, 08:50 PM
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Water hammer is caused by high velocity of the water right?
Water hammer commonly occurs when a valve is closed suddenly at an end of a pipe system, i.e. - washing machines.

As for the high pressure you have in your house, you'll need a PRV & expansion tank asap. Most fixtures are only rated for 75 psi and therefore will fail sooner at higher pressures.
 
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Old 01-26-11, 09:27 AM
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Originally Posted by VIPlumber View Post
Water hammer commonly occurs when a valve is closed suddenly at an end of a pipe system, i.e. - washing machines.
There are two conditions for water hammer: high velocity of the water in the pipe and sudden close of the pipe while velocity is high. At this high speed, water behaves more like solid than liquid so sudden stop causes it to compress suddenly creating shock wave that propagates down the stream.

If you have just have slow water coming through, no matter how high the static pressure was before the flow or high quickly you close it, water hammer doesn't happen because water behaves like liquid.

So closing the valve in theory should help eliminating the water hammer but it doesn't change the static pressure level, which may still be an issue for some fixtures.
 
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Old 01-26-11, 10:38 AM
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Originally Posted by VIPlumber View Post
Most fixtures are only rated for 75 psi and therefore will fail sooner at higher pressures.
Do you have any data about this? The way I understand is that most fixtures are tested at 120psi or so. I know my water heater is rated at 150psi.

I will install PRV if it is really necessary but based on the fact that the previous owner didn't have it and lived for many years tells me that the current static pressure level is ok as long as I can deal with water hammering issue. I do enjoy the high pressure when running a lawn sprinkler in the summer though. It covers pretty large area thanks to it.
 
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Old 01-26-11, 10:54 AM
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Check your actual pressure first...there are plenty of hammer arrestors you can install. Some require no plumbing skills at all.
 
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Old 01-27-11, 12:17 AM
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I would install a PRV 100% for sure! They are designed to keep the pressure in your home safe. Also as a side not most fixture manufactures (delta, moen etc..) will not warranty products if they house pressure is above 85psi. (same with your hot water tank)

I am not sure where you live but the water service to your house is pumped from the city they need to do this under high pressure to overcome hills etc.. so if for example at 2am you open your tap and all of the house around you have the water turned off it is possible to have water come in to your house at full city pump pressure (200psi in some cases) this can do very nasty things like shoot compression supply lines off! and cause a flood.
 
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Old 01-27-11, 06:07 PM
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You have to check your incomming pressure first to determine what your solution could be.
 
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Old 01-31-11, 09:43 AM
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So I've measured the pressure three times at different times of the day. It came out 80, 84 and 88 psi. So it's just above the cut off for PRV. So I'll definitely consider installing PRV but for now, I installed the water hammer arrestor yesterday and it seems to do the trick. The banging from the washer is gone at least

As for the lowering the flow rate by closing the main valve half way, I tried that and actually it made the water hammering worse. One thing I can guess as to why that is the case is the shock wave is trapped by the half closed main valve. So instead of propagating back down the main water supply, it sees that high impedance at the main valve and reflecting back. So I'm not going to try that any more:NO NO NO:
 
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Old 01-31-11, 10:17 AM
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See...you didn't need a Pro..just me...LOL. Only kidding! I've seen this question/problem so many times I almost feel like a plumber.

PRV's are relatively cheap and pretty easy to install with basic skills.

Glad you have identified and pretty much corrected the problem. Stay on it...that pressure can fluctuate up and down and cause issues.

Depending on your system...it would be nice to have your outside faucets before the PRV if possible.
 
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Old 01-31-11, 04:57 PM
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Originally Posted by Gunguy45 View Post

Depending on your system...it would be nice to have your outside faucets before the PRV if possible.
I know. I was just looking at it and that doesn't look easy unless I install two separate PRV's or repipe the faucets.

I'm tempted to install PRV and expansion tank by myself but a little nervous about soldering, let alone buying all the tools for it. So I heard about no-solder fitting like shark bites. Does anyone have any opinions about using those for PRV installations?
 
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