Why is my water pressure spiking to 120psi?

[uscpsycho]

I had no problem with my water pressure until the water department showed up about a week ago. They replaced my water meter and later that day I noticed my water pressure was over 100psi. I thought they did something wrong so I called and asked them to come fix it.

It stayed 100+ until they came the next day. They took a look and insisted my water pressure reducer was to blame and that their water meter wasn't the problem. They insisted that this problem started shortly after the meter was replaced was a coincidence.

So I installed a new water pressure reducer and set it to the mid 70's. It was fine for a few days until it spiked to over 100 psi. I thought that was weird because it's a brand new reducer. So I adjusted the water pressure back down to the mid 70's and last night it spiked to 120+. I caught it right away and adjusted the pressure back down to the 70's. This morning it spiked to 120 and within the hour came back down to the 70's without my intervention.

What in the world is happening? This is the reducer I am using. I just checked the specs and the maximum psi is 75. I just noticed this, so when I am reducing the water pressure to the mid 70's I am setting it to the reducer's maximum psi. Maybe I shouldn't do that? But doesn't 75 max mean that it should be impossible for the water pressure to ever go over 75? Is it possible I have a faulty reducer or is something else going on?

Please help me troubleshoot this, having my water pressure spiking so high is not good! THANKS!

 

[James Henry]

There's a chance they disturbed some sediment in the water line when they did the meter exchange. If you don't have a strainer before the PRV, there might be some trash fouling the PRV. That would explain 2 PVR,s failing.

 

[Sponsor]

 

[James Henry]

It's best to replace the pressure gauge first. If that's not it then you have a spare.

 

[uscpsycho]

Thanks.

The product description states it has a 20-mesh strainer screen. I assumed the screen is there to block debris?

If the problem is dislodged debris, what should I do? I don't want this to keep happening because these reducers aren't cheap. It's been seven days since the meter was replaced, is it safe to install a new reducer without having to worry about damage from debris? If not, what am I supposed to do so that I can install a new reducer without this happening again?

 

[uscpsycho]

It's best to replace the pressure gauge first. If that's not it then you have a spare.

I have two gauges reading the same thing. And one of the gauges is brand new, I bought it at the same time I bought the new reducer. So I don't think it's the gauge giving false readings.

 

[James Henry]

I personally would carefully disassemble the PRV without taking to much apart and inspect it for any debris, then I would try to flush it out. A new PRV should not act like that. You should be able to set it and forget it.

 

[Sylvan]

When your set pressure max is 75 in theory your outlet pressure should not exceed 75 Have you considered a sediment filter prior to the PRV

 

[James Henry]

If you haven't already, open and close a faucet for a few seconds then check the pressure and adjust the PRV by repeating the process.

 

[Bannerman]

I anticipate your PRV will be downstream from the meter, but best not to assume.

I suspect your new meter may now incorporate a back flow prevention device such as a check-valve which the old meter may not have been equipped with.

Cold water that enters a water heater will expand when heated. Because water cannot be compressed, that expansion will require additional physical space so the volume of the expansion will typically flow back into the town water main when there is nothing to prevent back flow. Although most PRVs will prevent back flow, some incorporate the ability to allow excessive downstream pressure to flow backward when the supply pressure is lower than the downstream pressure.

Depending on the supply pressure to your PRV and assuming your PRV has an ability to flow backward and also assuming the old meter did not prevent backflow, the expansion occurring within your WH will not have resulted in excessive pressure within your home's plumbing. If the new meter does incorporate back flow prevention, even if your PRV does allow back flow, the new meter will now prevent that from occurring so any amount of expansion will cause the plumbing pressure within your home to spike, regardless of the PRV setting.

If the pressure spike is caused from expansion occurring in the water heater, then a thermal expansion tank will be required within your home. Usually a small tank will only be needed as it will mostly contain compressed air that is separated from the water chamber by a flexible synthetic rubber diaphragm. With the compressed air precharge calibrated equal to the usual plumbing pressure, the tank will normally contain virtually 0 water, but any pressure increase caused by thermal expansion will cause the rubber diaphragm to flex to further compress the air charge to provide the space needed for the expanded water volume. When there is sufficient space available for expansion, the resulting pressure increase will be substantially reduced. Once any faucet is opened, then any additional pressure will be eliminated and the system pressure will return to the PRV setting.

When calibrating a PRV pressure, a faucet should remain partially open to allow a small flow of water, which will drain off any higher downstream pressure while calibrating the PRV to a lower pressure setting.

 

[Chucky_ott]

How or when are you measuring the pressure?

If you open and then close a faucet after a few seconds, does it remain high?

Do you have an expansion tank?

Could they have installed a check valve along with the meter? With a check valve and no expansion tank, your pressure may rise as the water in the heater warms up. It would be released once you open a faucet.

 

[Chucky_ott]

Yeah, what Bannerman said

 

[Jeff H Young]

install thermal expansion tank

 

[Breplum]

The mesh strainer should be protective enough to delete the chance of failure.
I only buy the 70XLs with the double union.
I have had more than two fail within a few weeks.
With the double unions, swapping out with a new one only takes a few minutes!!!
I then get credit for the defective one.

 

[uscpsycho]

I anticipate your PRV will be downstream from the meter, but best not to assume.

I suspect your new meter may now incorporate a back flow prevention device such as a check-valve which the old meter may not have been equipped with.

Although most PRVs will prevent back flow, some incorporate the ability to allow excessive downstream pressure to flow backward when the supply pressure is lower than the downstream pressure.

Depending on the supply pressure to your PRV and assuming your PRV has an ability to flow backward and also assuming the old meter did not prevent backflow, the expansion occurring within your WH will not have resulted in excessive pressure within your home's plumbing. If the new meter does incorporate back flow prevention, even if your PRV does allow back flow, the new meter will now prevent that from occurring so any amount of expansion will cause the plumbing pressure within your home to spike, regardless of the PRV setting.

The specs for the new PRV state: The direct acting integral bypass design prevents buildup of excessive system pressure caused by thermal expansion. The balanced piston design enables the regulator to react in a smooth and responsive manner to changes in system flow demand, while at the same time, providing protection from inlet pressure changes.

This is a lot of jargon but it sounds to me like the new PRV doe not prevent backflow. Is that correct?

I know my water meter was replaced because it was old. Is it safe to assume that the old valve likely didn't have a check valve and the new one likely does? Would a check valve be considered an upgraded water meter?

Yes, the PRV is downstream from the meter. If the new PRV doesn't prevent backflow and the new meter has a check valve, then does that explain the problem I'm experiencing? But I have an expansion tank so shouldn't that prevent the water pressure spike if the tank is working properly?

How or when are you measuring the pressure?

If you open and then close a faucet after a few seconds, does it remain high?

Do you have an expansion tank?

Could they have installed a check valve along with the meter? With a check valve and no expansion tank, your pressure may rise as the water in the heater warms up. It would be released once you open a faucet.

I am measuring the pressure with a Moen Flo (which is what alerts me to the excessive water pressure - I love this device) and then I used one of these on a hose nozzle to confirm, in case the Flo was giving incorrect readings.

I'm not sure if turning a faucet on corrects the problem. I know that turning the hose on and off while the gauge is on, then taking the gauge off (to clear the reading), putting the gauge back on, and then turning the water on again to test does not reduce the pressure. But in this case I am not really running any water through the system because the gauge doesn't allow water to flow out.

If the water pressure spikes again the first thing I will do is turn a faucet on to see if that fixes the problem. Assuming the problem is thermal expansion ,is there something I can do to force the water pressure to spike so I can test this?

I do have an expansion tank but the people that installed it were idiots and I have always wondered if it was correctly installed. I once asked my handyman to test it and he said it would be difficult. Would a plumber have an easier time testing it or is this going to be a challenge for anyone?

install thermal expansion tank

I already have one.

 

[uscpsycho]

The mesh strainer should be protective enough to delete the chance of failure.
I only buy the 70XLs with the double union.
I have had more than two fail within a few weeks.
With the double unions, swapping out with a new one only takes a few minutes!!!
I then get credit for the defective one.

I installed the one with the double union and it was truly a breeze to install even though I have never done it before. After I watched a couple of Youtube videos I had all the confidence I needed to do it myself.

What is this credit you speak of? The one I took off appears to be a 70XL but it looks quite old. Can I get something for it?

 

[Bannerman]

sounds to me like the new PRV doe not prevent backflow. Is that correct?

That is how I am also interpreting it.

Would a check valve be considered an upgraded water meter?

A back flow prevention device is for safety, to prevent a potential contamination situation in one home from back-flowing into the water main where it may contaminate other homes in the neighbourhood. Many municipal water systems have been adopting these precautionary devices at each point of entry. A check-valve is usually not actually part of the meter itself, but a separate component which is likely threaded directly to the meter.

As your home has a thermal expansion tank already installed, you can easily check its function yourself.

Shut off the main valve feeding the home and open a faucet to drain the plumbing system. The WH will not need to be drained. Once the water stops exiting the faucet, the expansion tank should be completely empty of water so assuming there will be some flexibility in the plumbing line connected to it, moving the tank should feel light with no water detectable.

On the end of the tank will be an air valve similar to a tire air valve. Using a tire pressure gauge, measure the air pre-charge in the tank. The pre-charge should be the same or no more than 2 psi below your intended PRV setting. If the pressure is lower, add air with a tire pump or compressor. If too high, release some air to the correct pressure.

If the diaphragm within the tank is broken, water will likely continue to remain in the tank after the system has been drained. Water may also exit the air valve, particularly if the air valve is directed downward. With a broken diaphragm, there is be no air pressure remaining in the tank once the system has been drained.

What is your concern with the expansions tank's current installation?

 

[Jeff H Young]

whether a check valve is at meter or not if you have 120 or 150 psi coming in to a reg set at 70 how does pressure stay at 70 when heating water? if you have high pressure you need a expansion tank in my opinion. Also is anyone sure that a "new" regulator wont creep over an extended period of time say 12 hours overnight. I would want to know exact cause as well but think the expansion tank is part of a basic modern plumbing system wher pressure is known to be high.

 

[uscpsycho]

As your home has a thermal expansion tank already installed, you can easily check its function yourself.

Shut off the main valve feeding the home and open a faucet to drain the plumbing system. The WH will not need to be drained. Once the water stops exiting the faucet, the expansion tank should be completely empty of water so assuming there will be some flexibility in the plumbing line connected to it, moving the tank should feel light with no water detectable.

On the end of the tank will be an air valve similar to a tire air valve. Using a tire pressure gauge, measure the air pre-charge in the tank. The pre-charge should be the same or no more than 2 psi below your intended PRV setting. If the pressure is lower, add air with a tire pump or compressor. If too high, release some air to the correct pressure.

If the diaphragm within the tank is broken, water will likely continue to remain in the tank after the system has been drained. Water may also exit the air valve, particularly if the air valve is directed downward. With a broken diaphragm, there is be no air pressure remaining in the tank once the system has been drained.

What is your concern with the expansions tank's current installation?

I've attached a photo of my expansion tank. There is a flex line from the water heater to the expansion tank. But before the flex gets to the expansion tank there is a fixed pipe and that same pipe goes into the wall. The way it's installed there is no way to move the tank to test if it is full or not. Was it installed wrong?

My original concern with the tank's installation is that it was installed without any air added to it. If no air was added, would that cause the pressure spikes I am having? But now I am also concerned that the tank was not installed correctly because it is not as you describe.

 

[Reach4]

I've attached a photo of my expansion tank. There is a flex line from the water heater to the expansion tank. But before the flex gets to the expansion tank there is a fixed pipe and that same pipe goes into the wall. The way it's installed there is no way to move the tank to test if it is full or not.

Drop the water pressure to zero. If the tank is good, the precharge will push all of the water out of the tank. If the tank is good, it will sound empty when you rap on it.

Ideal air precharge is the highest pressure that the city delivers.

 

[Bannerman]

The installation appears OK other than the lack of access to the tank's air valve. For me, I would be tempted to drain the home plumbing and unthread the tank so as to confirm the air pre-charge.

If the pre-charge is too low, the tank can fill with water even at normal pressure which may result in insufficient space remaining to absorb any additional expansion. If the pre-charge is too high, the system pressure will need to rise above the pre-charge pressure before any water will enter the tank.

When the pre-charge is equal to the pressure setting on your PRV, the tank will normally remain empty. Any water entering the tank while the system pressure is elevated will be returned back to the plumbing system when the system pressure is again reduced equal to the PRV setting.