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MrSmythe 08-24-2010 07:21 PM

Is 1/2inch pipe causing problems?
In the process of installing a pressure regulator on my main the other day, I decided to check under the house and see what was going on as we've been having really bad water hammer issues when sprinkler valves turn off, cold water in kitchen turns off, and sometimes when toilet flushes. I found that the main line comes in 3/4inches and remains so for about 10 feet under the house...then it branches off to 2 half inch lines (hot and cold) on the left and 2 to the right (bathroom and kitchen). the bathroom is a few feet away from the split. the kitchen though is about 50 feet away and that whole run is 1/2 inch. In the kitchen there is a sink, and a washing machine. Our PSI now that the regulator is on is at 60. It was at 90. We still get the water hammer.

Should I have the 3/4 inch line continuing closer to the kitchen, then branch off individual 1/2 inch lines for the washer and for the sink? Or should I bring the 3/4 inch line closer to the kitchen then keep the kitchen sink and the washing machine daisy chained as is? OR should I just leave the layout alone and maybe get a water hammer arrestor?

This water hammer issue is getting really annoying and i'm almost afraid to use the sprinklers because of the loud BANG that occurs when 2 of the 5 sprinkler valves closes. What should I do?

Just Bill 08-25-2010 06:14 AM

There are hammer arrestors than can be installed throughout the house. The simplest, which needs periodic freshening, is a verticle piece of pipe(usually 3/4) where the water line enters the house. Maybe 2-3' high with a cap on top, it is full of air and acts as a shock absorber. They do get water logged over time(years) and have to be opened up and re-aired.

Going from 3/4 to 1/2 too soon in the line can cause supply and pressure problems, but does not cause hammering. Ideally, the line should remain 3/4 until it reaches a fixture.

MrSmythe 08-25-2010 12:40 PM

Thanks Bill. I don't have room to put a vertical pipe like the one you are suggesting without busting open walls. The crawlspace is pretty short.

I was thinking of getting new sprinkler valves because I hear the Rainbird PGA has a slow closing valve that prevents water hammer, unlike the cheapy ones I have now, but that seems a bit expensive (5 valves to replace) compared to installing an arrestor or two. Problem is, the store-bought arrestors they have at HD look like they will only go onto a copper line, or the one for washing machines. Can either of these be used on PVC? There are two long stretches of PVC underneath the house that go to the two sprinkler "zones". Can I just put an arrestor inline on each of these?

braindead 08-25-2010 05:53 PM

Don't even think of putting on home made hammer arrestors, a total waste of time.

Your spinkler system is probable your main cause of your noise in the pipes, you need to install arresters as near the valves as you can.

Another spot is your wash maching valves.

You can also get water hammer from loose pipes or loose washers in a valve

MrSmythe 08-25-2010 06:06 PM

Do they have any arrestors that I can use for this at HD or Lowe's? The only one's I've seen either say they're for washing machines or they are 3/8" and I have a 3/4" PVC pipe going to my sprinkler valves.

What specific arrestor would you recommend and what is the proper way of installing it in a 3/4" pvc line?

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