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Thread: Severe water hammer/slow close valves

  1. #1
    DIY Member slb's Avatar
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    Default Severe water hammer/slow close valves

    Our back yard lawn sprinklers make a loud banging sound whenever they shut off. It's been this way since we bought the house four years ago, but I just now got around to investigating. I now realize that we are experiencing severe water hammer. There are eight sprinkler heads on one anti-siphon valve (too many?). I tried reducing the flow, but to significantly reduce the hammer, the flow had to be so low that the lawn was not being watered properly.

    I did some research and found some Hunter valves (type HPV) that claim to close slowly to eliminate water hammer. Do these work? Any other suggestions (other than digging up the lawn to add zones)?

    Regads,
    Steve

  2. #2
    Retired Defense Industry Engineer jadnashua's Avatar
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    Put in an arrestor near the supply.
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

  3. #3
    DIY Member slb's Avatar
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    The local hardware stores only have the small arrestors with compression fittings for use with dishwashers and icemaker hookups. Can you recommend an arrestor for use with sprinkler systems?

    Regards,
    Steve

  4. #4
    DIY Senior Member captwally's Avatar
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    The cure may be more simple than you realize. However, it does involve disassembly of the valve that is hammering. Irrigation valves are of a diaphraghm type that use the water pressure to close it, and an electric solenoid to open it. The water pressure must bleed to one side of the diaphragm to force it closed, and if the rubber is old and stiff, it can cause the effect you are seeing. If the orifice through which the water pressure must bleed to force the valve closed is restricted by debris, you can also see this happen.

    Note the brand and model of the valve, and ask your local irrigation supply house for a rebuild kit. There are typically about six stainless screws that hold it together, and rebuilding is quite an easy DIY project, if you pay attention and use common sense. Good Luck!
    Measure Twice, Cut Once
    Wally

  5. #5
    DIY Member slb's Avatar
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    Thanks Wally. The anti-siphon valves are Orbit brand. They look like the same valves that sell <$10 at the local HD. I'll see if I can locate a rebuild kit, but it might be easier just to replace the whole valve. Are some brands better performers than others (I can buy Toro, Lawn Genie, Orbit and Champion valves locally and other brands on-line)? Any experience with the Hunter valves I mentioned above?

    Regards,
    Steve

  6. #6
    DIY Senior Member captwally's Avatar
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    Good deal, sib. The realm of irrigation pieces, parts and accessories can be a confusing one, and it's all about the almighty dollar. you are correct in that an "Orbit" valve is basically an economy brand manufactured exclusively with price in mind, not quality.

    Hunter, Toro, RainBird, etc are all GREAT products but be careful! The stuff they sell at your local Home Improvement Warehouse store are not of the same quality as what your lawn irrigation professional uses. Typically the commercial products aare manufactured here in the USA to a very high standard of quality (and obviously a higher price tag.) And the cheaper ones are mass produced overseas by some poor guy making $12 a year, and sold to the large retail chains for more profit and the fact that many people will buy it simply because it is less expensive, though it does have the High Profile name. A few extra dollars are well worth it in a case such as this. Best to find a commercial supplier who will sell to the public. Good Luck
    Measure Twice, Cut Once
    Wally

  7. #7

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    If you can't find anything locally there are several suppliers on the net.

    Paul

  8. #8

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    You may need a pressure reducing valve to slow down the speed of the water through your pipes. You really should'nt have more than 50 psi to the heads as that is generally the optimal pressure for rotors and sprays. Water travelling to fast will also damage you pvc fittings and valves over time.
    Hope that helps.

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