# Water hammer



## The Walri (Nov 27, 2018)

Recently got my irrigation system up and running for the first time since moving into this house. Was running a full cycle from the controller for the first time and notice a pretty good water hammer when it switched from Zone 4 to Zone 5 (furthest from valve box). The water hammer made water surge out of the backflow preventer which worried me until I read that that will happen in these instances. When either zone is operated manually (via the controller) the water hammer doesn't happen. right after it happened I ran ran zone 4 for a minute and had it move automatically to zone 5 and no hammer. then two days after it happened the first time (with no cycles being run because we had rain) I turned it on today and it did the same when cycling from zone 4 to 5.

Both zones have 4 rain bird 5000's w/2.0 nozzles as do 4 other zones (that operate fine). I get what is causing it to happen, the sudden rush of water to zone 5 (I think) displacing air and then sending a shockwave back through the line when it reaches the end. but why isnt it doing it if I run that zone by itself, or after it just happened and I rerun the zone 4 to 5 transfer?

Is water draining from zone 5 after it hasn't rain for some time? creating a hammer the next time it runs? am going to try running just zone 5 tomorrow after not running it for a while and see what happens, or is it the more likely the abrupt shutting of zone 4 and immediate opening of zone 5? would programming a delay between zones help?

P.s. I'm on city water with pretty good pressure (have not measured it though).

Any thoughts on what to try eliminating this? Would switching the zone wiring so that zone 5 runs after a different zone help?


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## The Walri (Nov 27, 2018)

tested yesterday and the water hammer/backflow surging happened even when I turned that zone on first using the controller. and then again when it cycles around to it again when I ran the whole program. would a variable flow value help this?


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## CenlaLowell (Apr 21, 2017)

I'm wondering why the water hammer happened???

Also couldn't you put a hammer resistor in the line to prevent this???


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## Lust4Lawn (Aug 4, 2020)

Do you happen to have a hose bib on the line feeding all of the zones?


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## The Walri (Nov 27, 2018)

yes there's a hose bib before the backflow preventer (on the supply side)


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## SOLARSUPLEX (Aug 4, 2020)

Could this be related to the way the valves are organized in the manifold causing a hard stop from supply while 4 closes and 5 opens? This would make it seem that zone 5 is the issue when actually the issue is just the hammer coming from the supply against the zone 4 valve closing?

Can you set any kind of overlap from 4 to 5 so neither of them are closed at the same time while the system is running?


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## The Walri (Nov 27, 2018)

I dont think I can set an overlap on the timer but Older Rainbird ESP-M. but I think I can program a delay to space out the time between zones. Also it seems to be more intermittent, not happening every time now.


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## Lust4Lawn (Aug 4, 2020)

The Walri said:


> yes there's a hose bib before the backflow preventer (on the supply side)


Well since you have a hose bib you can use some type of suppression.

Forget the Sioux Chief units. They will not last even a full season if it has bad water hammer. I provide a link below to a unit that uses a diaphragm that you can pressurize the back side of to get the level of suppression you may need. I'd use these personally and they work very well.
https://www.supplyhouse.com/Watts-0121227-1-2-LF150A-Water-Hammer-Arrestor-Lead-Free


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## The Walri (Nov 27, 2018)

the hose bib is before the backflow preventer on the supply side...would installing it there regulate the surge going out to the system and prevent the hammer? I thought the issue was the pressure wave from the water rushing into the new zone and then sending the shockwave back to the backflow preventer? i.e. the problem was on the yard side of the back flow preventer?


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## Lust4Lawn (Aug 4, 2020)

Try opening the hose bib 10, 25, 50% and cycling the valves. See if there is a difference.


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