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Old 03-08-2010, 11:15 AM   #1
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Water pressure surge

In the last 6 months or so we have noticed that after one of us takes a shower, there tends to be a significant water pressure build up. If we do not run water through any other faucet in the house, the shower head will begin to leak after about 5 minutes, then it stops. If we run the sink after a shower there is a surge of water pressure and then it levels off.

We do not have a well.
I have not checked the pressure from the street or in our house.
I dont' know if we have a prv, but I am pretty sure we do.
There is a small tank above our water heater which I think is a reducer?

I am sure the leaking of the shower head is from the extra pressure on the shower gaskets, but any ideas what is happening to the pressure here?

Is it plumber time?


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Old 03-08-2010, 04:24 PM   #2
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Water expands slightly when heated. The tank above the water heater acts as an expansion chamber to prevent pressure from building up when there is a backflow preventer that keeps the expansion from going back to the water main.

The pressure tank could be saturated (no air cushion left). Then, since water does not compress, abnormal pressure builds up as the next tankful of water in the water heater is heated. Just after your shower, the water heater has probably kicked on, thus you noticed leaking then. The little pressure tank would then need to be drained, and then turning the water back on will probably achieve a reaonable balance of air and water in the pressure tank.

Modern pressure tanks have bladders to keep the air cushion from being absorbed. They come with instructions on how to pre-pressurize them, or if you can empty the pressure tank of water and then close the air valve on top, that will also achieve an acceptable cushion. Without a bladder, the tank needs to be emptied manually every few months. A tank with a damaged bladder will still work but also needs to be emptied and emptying may be more difficult compared with a bladderless tank.


The good conscientious technician or serviceperson will carry extra oils and lubricants in case the new pump did not come with oil or the oil was accidentally spilled, so the service call can be completed without an extra visit.

Last edited by AllanJ; 03-08-2010 at 04:45 PM.
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