Water Pressure Question

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Old 01-21-11, 06:57 AM
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Water Pressure Question

Hello -

I have discovered that when I come home from work (house is vacant for 8+ hours) and turn on a faucet that there is an initial burst of water pressure (more than usual) it only lasts for a few seconds then returns to the normal water pressure. Is there a reason for this?

I live in PA, so it has been cold here the last few weeks (when the problem started). So I thought it might have something to do with the temperature. I have a newer house (8 years old). Can anyone help me with this issue?
 
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Old 01-21-11, 07:15 AM
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Most likely your water heater is firing in the morning and raising the pressure in the lines. If you have an expansion tank already installed..it may be waterlogged and not absorbing the extra pressure.

If you are on city water and have a Pressure Reducing Valve (PRV) it could be leaking past very slightly during the time of no use.
 
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Old 01-21-11, 08:59 AM
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OK - I am on City Water, not sure if I have a pressure reducing valve (I think I do though) will look when I get home.

Is this an issue I should be concerned about?
 
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Old 01-21-11, 09:32 AM
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It would be something you should address...yes. You can get a pressure gauge to screw onto an outside hose bibb (if it is after the PRV...some are before) or clothes washer supply for about $10. Normal pressure would be in the 45-60 PSI range...though slightly higher is not normally an issue, much higher can cause failure of plumbing connections. One of the worst is when a compression style supply line for a toilet pops out. The valve is normally pointed up and will spray water all over the room.
 
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Old 01-21-11, 06:56 PM
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Kappadoce:

What you're observing could also happen if you've had your water meter replaced recently. You see, lately there's been a lot of fuss over "cross contamination" whereby contaminated water gets BACK into the city water supply piping because of a reversal of pressure. For example, say you were filling a small swimming pool with a garden hose when someone else's house down the street caught fire. The fire truck might be able to suck water out of the city water supply lines at a higher rate than the city water piping can deliver water. In that case, there could be a pressure lower than atmospheric pressure in the city water supply piping, and water from your swimming pool could end up flowing backwards into the city water supply piping.

To prevent this from happening, all new water meters have check valves built into them which prevent such back flow. Older meters simply allowed any pressure increase that occured in the water heater when the water was heated to simply leak back through the water meter. New water meters don't allow that backflow, and so that may be the cause of the problem.

"I live in PA, so it has been cold here the last few weeks (when the problem started)."

And, that may be the entire cause of the problem as well. You see, not only does cold water expand more when heated than cool water, but colder water contains a lot more dissolved oxygen (which is what fish breathe). When that colder water goes into your water heater and gets heated up to 130 or so deg. F, then not only do you have more water expansion than you would have had with cool water, but you also have more oxygen bubbling out of solution. The oxygen bubbles that form occupy space in the water heater that raises the pressure inside the heater.

So, it's very possible that the higher initial pressures you're experiencing are due to the colder water being supplied to your water heater and that the problem will correct itself as the weather warms up. Still, it would be a good idea to buy a pressure gauge you can connect to your water heater's drain valve or your washing machine's supply valve(s) to diagnose the problem.


Regarding the pressure reducing valve, look around where the water supply pipe comes into your house for a valve that looks something like this Watts pressure reducing valve:



In areas where there are a lot of hills, the water pressure has to be higher so the people living at the tops of those hills have good water pressure. But often, that means that the people living at the bottom of the hill have excessively high water pressures. To address this problem, the people at the bottom of the hill will have a pressure reducing valve that reduces their 100 psi water (say) down to 50 psi. The pressure reducing valve will have an adjusting screw on top, but NEVER adjust that screw until you first check to see that the strainer screen isn't clogged.



That's because people will adjust their water pressure using that adjustment screw only to find out that adjustment didn't do any good. Then they discover the valve isn't working properly because the strainer screen is clogged up. Now, even after cleaning that screen, their water pressure will be off because they changed the adjusting screw setting.

Look for some sort of shut off valve down stream of that pressure reducing valve. There should be one so that the pressure reducing valve can be replaced if required. Try closing that shut off valve before going to work in the morning, and then opening it again as soon as you get home from work. That will prevent the pressure building up in your piping because of a leaking pressure reducing valve. Test to see if there's a pressure surge when you first open a faucet. That will tell you if your pressure reducing valve is leaking (as would a pressure gauge on the hot water heater's drain valve or on one of the supply valves to your washing machine.

If you find your pressure reducing valve is leaking, then you don't have to replace the valve. You can buy overhaul kits for most pressure reducing valves that allow you to replace all the wearing parts on the valve.
 
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Old 01-25-11, 11:46 AM
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Nestor - Thank you so much for this in-depth answer. I found the main supply and have a pressure valve that looks exactly as the picture you posted. I did not have a new gauge installed, so I do not think that is the problem.

The order of components on the main supply pipe is follows:
Shut Off Valve >> Pressure Reducing Valve >> Another Shut Off Valve >> Water Guage >> Another Shut Off Valve

Also- as gunguy45 mentioned it could be the water expansion tank. I looked and I do have one coming off of the water heater.
 
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Old 02-03-11, 12:39 PM
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Nestor - I tried the test you suggested to shut off the valve after the Pressure Reducing Valve for a day. After I came home, I turned the valve back on and tested a faucet, there was not a pressure surge.

So I am thinking that, to gunguy45's point that it could be the water heater expansion tank is waterlogged? How would I relieve that pressure??
 
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Old 02-05-11, 04:59 PM
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I've never had a tank, so don't take this as gospel and WAIT for other info from the Pros...but as I understand....you shut off the water, open the drain on the tank if it has one, then apply air pressure to the schrader valve (like a tire stem) equal to the pressure of your water (ie..45 lb water pressure..45 lb air pressure).

Oh...before any of that..try releasing pressure on the schrader, just like you would a tire...if you get water..the bladder has failed, or it never had one and is a less preferred option vs the bladder tanks.

Good info here as well...check around.. see what some of the instructions say.. Potable Water Expansion Tank Sizing - Support - Water Safety & Flow Control -Watts
 
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