Water hammer

[King3244]

I have a water hammer problem but only when the taps are opened not on closing.........same thing or different? For instance when the toilets flush we will get a bang but not after they have finished filling, likewise the hammer comes when the washing machine is filling but not when it stops.

I have a pressure reducing valve as the water coming in from the district is 185 psi. We have it reduced to 65 psi.

The water tank is a tankless and there is no expansion tank.

Any help would be greatly appreciated. As a note.......I did a search on the site and read everything I could but nothing seems to cover my problem.

Thanks, king

 

[Cass]

Get a pressure gauge and check the water pressure B4 you do anything. The PRV may be bad. That (185#) is very high pressure an dcould be causing the noise if the valve has failed. Be sure the gauge will read up to 200#.

 

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[Pewterpower]

THat's some hella psi. I bet your showers are awesome!

 

[Cass]

Had a customer once whos toilet fill valve kept coming on. I thought it was a bad flapper. Nope, The pressure was 197 and it was forcing the fill valve open.

 

[Jadnashua]

One of the pros may offer comments, but I think I remember reading that when the water pressure is that high, it isn't a bad idea to have two prv's in series. I'm not sure how well they work trying to drop that great of a delta in pressure in one stage.

 

[King3244]

Thanks guys, I will check the pressure again..........I had it checked about 1 1/2 years ago but I never thought about a prv going bad. There is no noticeable difference to the volume or the pressure coming out of the taps.

The reason the pressure is so high is that we live in a mountainous area but we are down by the lake so we get a lot of head pressure due to elevation changes........that old 1/2 pound per foot adds up in a hurry.

I still don't understand why it hammers on opening and not closing?

King

 

[King3244]

Oh and one other thing thanks to jadnashua.........we do have 2 prvs.........one by the street connection and another one in the house.

King

 

[Cass]

With that kind of pressure I would install 2 PRVs and I would install 3 pressure gauges. 1 showing street pressure, 1 between the 2 PRVs showing intermediate pressure, and 1 after the 2nd PRV showing house pressure. The 1 showing street pressure should have a top pressure reading of 250 or 300#