Main Drain Suction

[NFLJACK]

When I dive to the bottom of the pool, I don't feel any suction in the main drain -- nothing. Is something wrong?

Thanks.

Jack

 

[jblizzle]

Welcome to TFP!!!

That is pretty typical ... they are designed that way to prevent entrapment. Of course whether you have flow through there or not is dependent on your plumbing and valving.

 

[Richard320]

Hi, Jack!

That's pretty typical. Even when I have mine on full, it doesn't feel like anything.

Do you have a valve to open and close the main drain? If not, do you have two holes in the bottom of the skimmer?

 

[BuckeyeChris]

i just tested my own main drain over this same concern. I thought perhaps the skimmer/main drain ratio valve was installed wrong. But after moving it full one way and putting my hand in the bottom of the skimmer, under the venturi return, and then full the other way and having no suction in the skimmer, it's clear the valve is correct. I also folded up a bouganvillea leaf (no chance I spelled that right) and shoved it through the main drain grid. Got out of the pool and looked in the filter that is just before the pump and the leaf was in there.

However, I can see a bunch of sediment accumulated in the ring of the main drain; the suction isn't strong enough to actually carry it around into the input ports of the drain. I'll probably have to get a vac attachment down there every once in a while to clean it out.

 

[NFLJACK]

Hi, Jack!

That's pretty typical. Even when I have mine on full, it doesn't feel like anything.

Do you have a valve to open and close the main drain? If not, do you have two holes in the bottom of the skimmer?

Thanks for the responses.

Yes, there is a valve where I can cut off either the skimmer or the main drain. I cut off the skimmer when I felt for the suction on the main drain.

In the skimmer, there are two holes; however, one is plugged up with some sort of cap.

Perhaps I'll take a colored leaf and poke it in and see what happens.

Thanks.

Jack

 

[Richard320]

Thanks for the responses.

Yes, there is a valve where I can cut off either the skimmer or the main drain. I cut off the skimmer when I felt for the suction on the main drain.

In the skimmer, there are two holes; however, one is plugged up with some sort of cap.

Perhaps I'll take a colored leaf and poke it in and see what happens.

Thanks.

Jack

Other ways to test it are: swim down with a bottle of food coloring and see if it gets sucked in. Or switch to full main drain suction and set a rubber mat or something over it and see if it starves the pump and the return pressure drops to nothing.