Water Hammer

[pmark]

I'm trying to figure out what is the cause of a water hammer in my pipes and what to do to resolve it. The water hammer appears when I open th value that feeds into tmy sprinkler system. When that value is open, anytime any facut is open in the house, there is a heavy thumbing sound. I pinpointed the source of it to a checkvalue that is installed after the value on the pipe that feeds the sprinkler system. My theory is that the sound is from the value slaming open/close but I'm not sure.

Another thing that might be a factor is that house has 1/2" pipe, but the sprinkler system was added on later and uses 3/4" pipe. I'm not sure if this matters or not...

Anyway, does anyone know what I need to do in order to resolve this? I'll probably call a plumber to do the work, but I want to make sure that I understand what he will be doing.

Thanks!

 

[MagnusTheBrewer]

Here's a simple fix.

 

[C1]

Your hunch is right. Id modify the check valve (probably too strong a spring.) Another possibility is to change the house water pressure if you're running a regulator (eg, a Wilkins or Watts).

The check valve is no doubt anti-back flow. A guess is that with the house internal valves closed then opening the sprinkler circuit, the check valve opens. But now when one of the house internal faucets opens, then the pressure in the sprinkler line falls resulting in the check valve activating, at least partially and may, under circumstances, modulate.

A possibility is to pull the check valve apart and reduce the closing spring pressure.

 

[pmark]

Your hunch is right. Id modify the check valve (probably too strong a spring.) Another possibility is to change the house water pressure if you're running a regulator (eg, a Wilkins or Watts).

The check valve is no doubt anti-back flow. A guess is that with the house internal valves closed then opening the sprinkler circuit, the check valve opens. But now when one of the house internal faucets opens, then the pressure in the sprinkler line falls resulting in the check valve activating, at least partially and may, under circumstances, modulate.

A possibility is to pull the check valve apart and reduce the closing spring pressure.

Ok, I'll look into that. Thanks!

 

[z1ggy]

I know this might sound dumb, but is there any chance at all, that the water in the pipes could be hot enough to boil?

The only time I've heard of water hammers in piping, is from bubbles due to cavitation "exploding". Of course, this was not home piping, it was something different, so not sure if this applies.

 

[MagnusTheBrewer]

I know this might sound dumb, but is there any chance at all, that the water in the pipes could be hot enough to boil?

The only time I've heard of water hammers in piping, is from bubbles due to cavitation "exploding". Of course, this was not home piping, it was something different, so not sure if this applies.

The water can only be as hot as the water heater makes it. Most household water heaters aren't even capable of boiling water even if there wasn't a safety valve on the water heater that is rated to blow before the water can even get that hot. So, no, it is not possible unless you live above 15,000 feet?

 

[iamwiz82]

The water can only be as hot as the water heater makes it. Most household water heaters aren't even capable of boiling water even if there wasn't a safety valve on the water heater that is rated to blow before the water can even get that hot. So, no, it is not possible unless you live above 15,000 feet?

While a HWH can't boil the tank it's possible that they could boil a small portion (enough to generate steam). Steam in the pipes will cause noise, but not as how it was described.

 

[TheSlamma]

C1 clearly knows and understands pre-PVB sprinklers, I would try the things he noted.

My last house had double check valves 10 feet under ground for the system there, it caused a hammer until I installed an adjustable pressure regulator (house had no regulation at all)

 

[MagnusTheBrewer]

While a HWH can't boil the tank it's possible that they could boil a small portion (enough to generate steam). Steam in the pipes will cause noise, but not as how it was described.

I'm sorry but this makes no sense. a small portion of water is heated to boiling nearest the burner or element located at the bottom of the tank. That small portion then makes it's way to the top of the tank without losing enough heat to drop it below boiling to the surrounding water. Then, that small portion of boiling water makes it past the check valve placed there for this exact reason and finds it's way into the pipes. Let's totally ignore the fact that the entire house's hot water would be so hot as to scald anyone to begin with. None of this is logical.

I have seen many old houses with butchered plumbing and water hammer but, I have never seen or heard of a house with steam in the water supply pipes. In houses with radiators, there are sometimes issues with steam but the radiator system is not connected to the faucets.