Tankless and Water Hammer

[halogen25]

I have recently noticed water hammer when my outdoor sprinkler system cuts off. On closer inspection, I found our 6 month old tankless water heater to be the source of the noise. When the sprinklers shut off, there is a clanging from within the heater, and the pressure relief valve on the hot water side emits a small amount of water.

This is clearly a problem. Would the best way to deal with this be to install a pressure regulator in front of the water heater, or am I better off addressing the source of the water hammer? Any suggestions for this?

Thanks in advance for not trashing me for having a tankless.

 

[Cass]

You need to check the water pressure B4 you do anything.

 

[Sponsor]

 

[halogen25]

Last I checked, the water pressure of my house is 80 psi. The tankless has a rating up to 150 psi. Are you suggesting that I determine the pressure when it is hammering?

 

[Cass]

80# is a little on the high side. You may want to consider installing a PRV.

Average house water pressure is 50-65#. They also have water hammer arrestors that can be installed in line to deal with the hammering.

 

[Tbplumbloco]

water hammer

In my local area 80psi would be to high,in my opinion you need a PRV installed where your water supply comes into the house and possibly an expansion tank near the water heater.Water distribution from a municapality
is usually right around 50psi anything above that is harmful to your water piping and faucets.

 

[Cass]

In my local area 80psi would be to high,in my opinion you need a PRV installed where your water supply comes into the house and possibly an expansion tank near the water heater.Water distribution from a municapality
is usually right around 50psi anything above that is harmful to your water piping and faucets.

What harm would 55-65#s do that 50# wouldn't???

 

[hj]

pressure

We usually set the pressure to 75 psi. Below that people complain about the shower flow.

 

[Master Plumber Mark]

spring loaded check calave??

that does not sound all that high to me....

you could also add a spring loaded chceck valve into the

system as it goes into that tankless heater.....


just have to ask for fun

.....how is the tankless heater worked out for you so far???

 

[halogen25]

Mark, I honestly love it. Not a glitch, and an endless supply of hot water, especially when the in-laws visit!

But I realize that this option is not for everyone. We have a small house with very limited square-footage (which we made good use of after evicting the tank), and we put the tankless on the outside of the house right near the bathroom. A bigger house, a second bathroom (with shower), or more plentiful house/garage space would have made this an unwise (and expensive) choice.

 

[Mikey]

No matter what the average pressure in the system, a large flow suddenly stopped will generate a high-pressure pulse. Although the PRV and expansion tank on the water heater are excellent suggestions in and of themselves, I'd also install a large hammer arrestor right at the sprinkler valve to absorb the high-pressure pulse when the sprinklers shut down. It's likely other fixtures with mechanical shutoffs (e.g., toilets, washing machine) have arrestors near their attach points, but if the sprinkler system was added later, or is attached to a hose bib, there's probably no arrestor associated with it.