Suction side leak when running vac?

[gtnos]

I have 2 of the Doughboy Skimline Skimmers on my pool, one at each end. these are the type that have the hole below the weir for vacuuming, and you remove the lid and lay it in the bottom of the skimmer to activate the vacuum hole.

I plumbed a ball valve on each one near the pump so that I can turn one or the other off. When I hook up my Barracuda vac, after assembling and knocking out the air with the return, I hook up to the vac hole, drop the skimmer lid, and off it goes. I then close the other skimmer to double the suction to the vac.

the problem manifests itself when I close off the second skimmer. Air enters the pump filter basket and after several minutes, the basket will be half empty It does this no matter which skimmer I use. During normal operation, if I close one, it does not do this. only when vacuuming.

I did have a small one drip every 30 seconds water leak near the valve on one skimmer. I have fixed it. I also went around all the joints in the pipe (1.5 inch schedule 40 pvc) and liberally put more glue around the joints to ensure a tight seal. There is only 1 foot of pipe exposed under each skimmer and only a couple of feet near the pump for each one. The rest of the piping was buried 2 feet deep when I backfilled, so I cant check the whole system, but I cant imagine an air leak 2 ft underground pulling in any significant amount of air. It was all checked for leaks prior to back filling and I shoveled dirt under the lines manually before I back filled with the tractor to make sure the lines were not excessively exposed to the weight of the dirt being filled on top of them.

I have removed and replaced the pump filter basket lid more times than I can count and have lubed the O-ring.

whats the problem here? the vac works fine with both skimmers open, but it works even better if I close one.

thanks!

 

[duraleigh]

Since the system does not suck air in any configuration other than the one you are describing, I think you will have to modify that configuration. I would suggest hooking up the vacuum and then throttling down the opposite skimmer until it just barely starts to pull air into the pump basket. That will be your optimum setting and will not result in any loss of flow or effectiveness to speak of.


What I believe is happening is the motor on the pump is strong enough (and your intake capacity isn't adequate enough) to break the seal(s) on your intake..

I have this pictured perfectly in my mind but am having trouble choosing the words to make the explanation concise......let me stop right there and see if we are close to being on the same page.

That path will be a lot easier than trying to troubleshoot each and every seal which may or may not work anyway.

 

[gtnos]

basically, you are saying that my pump is outputting more water than it is capable of intaking due to it intaking it through such a small hole. that makes sense. so by only closing the other skimmer part way, to the point you describe, it equalizes everything out.

does that sound right? sounds good to me, ill give that a try.

thanks Dave!