SPRINKLER TALK FORUM - You Got Questions, We've Got Answers

Water Hammer can be calculated as a function of waterline length, as well as pressure, and the speed of valve closing, so the longer the line, the more the hammer force can be. Despite whatever pipes are banging in a house, the lawn sprinkler system itself isn't being damaged. If a system has a poly main line and high supply pressure, it would have pressure regulation, so supply line water hammer would be stopped at the regulator.

Now consider a golf course, with an old sprinkler system with large heads, without any check valves. Turn on a zone, and the water rushes at higher-than-normal speed while air is rushing out of the head(s) - when the air is finished rushing out, WHAM comes the hammer, and another head gets blown off the end of the line. Instead of refitting the entire golf-course system, they can use special control valves that will only open partially, until the air is pushed out, and the zone pressure comes up to a set point. (Cla-Val)

wetboots said, "Hammer isn't a factor on residential systems. You need big water supplies to have hammer worries"

care to elaborate?.......I find water hammer to be more prevalent on residential systems. Why would you need "big water supplies" to cause water hammer?

What I am doing is installing a drain valve at the lowest point of each circuit, and making sure ALL the pipes slope down hill to this drain valve. I'm also installing the Rainbird SAM check valves for all sprinklers except the highest one. That way, to winterize the system, I just open the drain valve. The only water left anywhere in the system is in the head itself after the SAM check valve. But if you can lift the pop-up at all, even that water will drain out quickly. The only difficulty is if you use Rainbird spray heads, they will pop-down flush with the top of the sprinkler and you'll have to unscrew the entire top off to get the water out. But in my case, I've decided to design my system for the MP Rotors - http://www.mprotator.com/products/MP2000/MP2000features.html These ever so slightly sit above the top of the sprinker body such that you can easily get a screw driver under the spray head to lift the pop-up manually to allow the water in the sprinkler head to drain around the SAM valve.

The check valves help reduce 'puddling' around the sprinkler heads are steep slopes, but are they absolutely necessary? No. You only need to pay the extra money for check valves if you feel it necessary.

They irrigated slopes long before there were check valve sprinklers, so there is no 'need' for them. Hammer isn't a factor on residential systems. You need big water supplies to have hammer worries.

I am replacing an irrigation system on a hillside with a gradual slope. Do I need to install sprayers with internal check valves? I heard that the internal check valves eliminate "water hammer" damage on the sprayers. What happens in winter? Will water trapped in the pipes cause more pipe ruptures? Thanks.