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Pressure Thump or Bang

My home was built in the late 60's and I recently put in a new Lawn Sprinkler system and when any of the automatic valves close I get a loud thump or Bang.

Can this pressure change or thumping put un-do stress on other plumbing components?

Can I eliminate or diminish this affect?

Some details: The main line from the water meter is 1" and then the feed drops to 3/4" in the house, garage, and splits to the water heater and cold supply and then feeds 1/2" pipes to the fixtures. The line to the sprinkler is 3/4", from the main cold, hot, split to a 3/4" Ball Valve, then 70ft though the house, then to an exterior hose bib, then to another 3/4" Ball Valve, then the 3/4" sprinkler manifold, there are no other feeds from this line. All copper, I do not have a pressure regulator or an expansion tank.


Re: Pressure Thump or Bang
scott_of_valencia wrote:

Can this pressure change or thumping put un-do stress on other plumbing components?..........

Can I eliminate or diminish this affect?...........

I do not have a pressure regulator..........


I had the same problem as you do.

Long story short but I discovered my water pressure was way too high when my meter was replaced and the guy that replaced it tested my pressure. I replaced the regulator and the problem went away.

I bought my replacement regulator from ACE hardware and the sales guy told me they rented water pressure meters..... Just screw it on to a hose bib and test.

I think 65 lbs or so is about right.

Just a thought. I ain't no plumber.

Re: Pressure Thump or Bang

Like NEC said, I'd check your water pressure first to make sure, anything over 80psi and I would recommend a pressure reducing valve. That's probably not the problem however, with quick closing solenoid valves, such as washing machines and powered manifolds, the water is shut off so fast it hammers the pipe reverberating throughout the system. Two options; install a mechanically-operated water hammer arrestor, or sweat a copper tee with the branch vertical on the cold main and 16" piece of 3/4 or larger with a cap going up(This is the air chamber). This trapped air will absorb the pressure change. The homemade version will get saturated over time. You can re-energize by draining the water supply lower than the air chamber, and filling back up. The closer either one is placed to the problem valve the more efficient it will work.


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