Water hammer when irrigation turns on

I have a 2.1 gal or so pre-charge tank with a submersible pump CSV valve. Everything is fine except when my irrigation first turns on. The water flowing into the irrigatation system causes the small tank to dishcharge rapidly and create water hammer. How do I solve this. My irrigation tees off the main at the well head. I have the standard backflow preventer on the irrigation system and the heads drain after the zone runs. Hope this makes sense. Thank you for your assitance.

You probably have too much air in the pressure tank. You want about 5 PSI less air than the start pressure of the pump.

I was given that suggestion by my pump installer and it did not make a difference. It seems the water disharges quicker than the pump can begin pumping. This happens very quickly and then everything is just fine.

We use water hammer arrestors for commercial plumbing quick closing valves such as solenoid or even flush valves for toilets. A plumbing supply house should have these, maybe even Lowes or Home Depot. In the old days they used a section of pipe filled with air which worked but eventually became water logged. The water hammer arrestor has a bellows or piston inside which absorbs the "shock" created. These are relatively inexpensive.

If your irrigation is not Teed off after your pressure tank, when the pump is off, the water flow from the tank back to the irrigation is flowing toward the pump when it comes on, that can cause water hammer as the water flow has to stop and then be turned 180* back to the tank.

gahlen said:

I was given that suggestion by my pump installer and it did not make a difference. It seems the water disharges quicker than the pump can begin pumping. This happens very quickly and then everything is just fine.

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OK then your lines are empty when the irrigation starts. It takes a lot of water to fill the lines before the pressure starts to build. Your sprinklers are probably down hill from the zone valve, so they drain out every time the irrigation shuts off. They make little check valves with a 1.5 or 2 pound spring that you can install before the sprinkler head. These will keep the line from draining out. Then you won't have to wait for the lines to fill, and the pressure will come up quickly.