Water Hammer Arrestor Advice Needed

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Lance Roberts

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I wish I had the ability to search posts instead of having to read through them all to find the correct topic as I'm sure this question has already been answered. I need to install a water hammer in my piping, and I'm trying to find a more permanent solution than the Sioux Chief arresters I've been getting from Home Depot. When I install them at the washing machine, the pipes are quiet for the first few months, but after that the noise gets progressively louder. By about a year's time, even closing the bathtub faucet will cause loud banging of the pipes.

Is there a more robust brand that will give me a longer lifespan or do I have to keep replacing the arresters every year? Should I look to install the arrestors in more than one location or is the washing machine enough for the entire household plumbing?

Also, my house was built in 1962. Should I be looking into a plumbing upgrade after so many years or am I okay as long as there are no glaring problems?

Thanks!
 

Jadnashua

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To work to their best advantage, a water hammer arrestor needs to be placed as close to the quick-closing valve as possible. I actually have mine attached to my WM, and then the hoses connect to them rather than at the shutoff valves on the wall. The hammering is caused by inertia...water doesn't compress. Moving water has inertial energy - it wants to keep moving. The valves on the WM turn off VERY quickly, and an arrestor has a moving piston and sealed air chamber that allows for a 'soft landing' or motion of that water column. There are some brands that utilize a synthetic rubber bladder (like an air bag) rather than a piston whose seals could wear out and let it fill with water (a bladder type will eventually have a failed bladder, but the piston types generally last longer). But, keep in mind, if your pipes weren't properly supported throughout the house, shutting a slower acting valve could also allow the pipe to move and literally hit something.

Before I went further, I'd go buy a water pressure gauge with a second, tattle-tale hand to show peak pressure. My guess is that your normal, static water pressure is excessive. By code, at least in the USA, your static water pressure should not exceed 80psi, and many people live quite happily with it much less. Drop that down with a pressure reduction valve and install an expansion tank so the reheating of water in the WH doesn't open the T&P safety valve, and you may solve both your initial problem and the longevity of the arrestors you have been using.
 

Lance Roberts

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To work to their best advantage, a water hammer arrestor needs to be placed as close to the quick-closing valve as possible. I actually have mine attached to my WM, and then the hoses connect to them rather than at the shutoff valves on the wall. The hammering is caused by inertia...water doesn't compress. Moving water has inertial energy - it wants to keep moving. The valves on the WM turn off VERY quickly, and an arrestor has a moving piston and sealed air chamber that allows for a 'soft landing' or motion of that water column. There are some brands that utilize a synthetic rubber bladder (like an air bag) rather than a piston whose seals could wear out and let it fill with water (a bladder type will eventually have a failed bladder, but the piston types generally last longer). But, keep in mind, if your pipes weren't properly supported throughout the house, shutting a slower acting valve could also allow the pipe to move and literally hit something.

Before I went further, I'd go buy a water pressure gauge with a second, tattle-tale hand to show peak pressure. My guess is that your normal, static water pressure is excessive. By code, at least in the USA, your static water pressure should not exceed 80psi, and many people live quite happily with it much less. Drop that down with a pressure reduction valve and install an expansion tank so the reheating of water in the WH doesn't open the T&P safety valve, and you may solve both your initial problem and the longevity of the arrestors you have been using.

Not sure if I'm posting my reply in the right place, but thanks for the tip on the water pressure. I'll head to Ferguson or something to see if I can get one. I don't have an expansion tank because I have a tankless water heater. Hopefully the water pressure isn't compromising that unit. I'll also move the arrestors to right on the washing machine to see if that will give me any immediate benefit.

Next weekend should be interesting.
 

Jadnashua

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A tankless system isn't likely to cause enough of a problem since it shuts off when you stop running the water...most of the big box stores carry a pressure gauge, can get one to you in a couple of days. OFten, the easiest way to use it is to get one with a hose connector on it. Then, you could hook it up to the washing machine supply or an outside hose bib, or almost anywhere with adapters after you unscrew the aerator on a sink valve. If your pipes aren't anchored, it doesn't take much for them to bang against a wall or something similar.
 
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