multiport valve question

[Lmlduradenali]

Hey guys so I have a bad multiport valve on my system which is Hayward, and replace with a whole new head today.

Works flawless and seems great... do have a question about a minor noise I seem to get after I did the backwash....

So I backwashed, turned pump off , rinsed, turned pump off and then turned back to filter, snd I can feel some pressure build up when going from rinse to filter... normal????

All this is when the pump is off

 

[JamesW]

If you’re getting a “bang” and the waste is hard plumbed, then it’s probably “water hammer” from the valve suddenly stopping the flow of water going to waste. You can remove the sight glass before rotating the multiport back to Filter or install a vacuum breaker on the waste line.

 

[Lmlduradenali]

Got ya...

Can u explain a little more???? Like a pressure release valve on the waste line???

 

[JamesW]

Assuming that you have a hard plumbed waste line, the water flowing through it gets stopped immediately when the valve goes back to filter.

If you use a vacuum breaker on the waste line, it allows air into the line when a vacuum is created by the water suddenly getting stopped.

Google in-line vent, cheater vent, mini vent, air admittance valve etc. Any hardware store will have them.

You put a T on the waste line and a female adaptor that you can screw the mini vent into.

OATEY Sure-Vent Installation - Eliminate the Vent Pipe! - YouTube