Help! Boo-boo in pre-closing: pump lost prime after backwash

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Water_man

Water_man

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Jun 7, 2008
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Brookline, MA
Tomorrow (Friday) my pool pro is coming to close the pool so I started prepping whatever I can do on my own before he comes. Water temp has reached a good 55 so it’s ready to close. I brushed off and collected all the tree debris and acorns from the solar cover. I figured that later on I’ll vacuum-clean the bottom from any leaves that may have fallen in. Connected the vac line through the skimmer suction opening. Vac was OK and pump was pumping as usual.
Then I added liquid chlorine for shocking and circulated the pool for good 2-3 hours.
Then I started pumping water out using an immersion pump. In order to expedite the process of the partial draining I also started a backwash. Everything worked fine until the pool water level fell below the skimmer entrance level. The pump lost its prime.
I couldn’t get suction at the suction hole at the bottom of the skimmer.
I still need the pump in order to vac-clean the pool bottom. Why did the pump lose prime and what should I do?
 
I take it you have an AnthonySylvan. I do, too. The Vac in to skimmer connection where you just put the cuff into a hole in the skimmer sucks in an awful lot of air if water is not flowing in to the skimmer from the pool. You probably could maintain prime for a few feet below the skimmer if you screwed a vac nipple into the suction hole and pushed the cuff onto that. It is a much tighter seal that way.

I can't tell you if you could do that now and restart without putting water back into the pool. It would depend on a lot of things, especially the drop between the skimmer and the current water level. But you could try taking a hose and filling skimmer while letting air out the pump basket cover. Then fill vac hose with water, slap it on the nipple and fire up the pump (helps to have a helper). Make sure all other suction lines are closed...but you knew that. Also, if you have a hose with one swivel cuff, make sure that is on the vac head end, not the skimmer end. Those babies leak a lot of air in if they are above water and can kill prime.
 
Thank you, Durk, for your quick response. What you’re saying about the leak between vac hose cuff and the skimmer hole has a strong circumstantial evidence, but I don’t understand why the connection sucks air if water isn’t flowing through the skimmer. If the water covers the skimmer line, this connection maintains vacuum, so what changes when the water level in the skimmer drops? Anyway, although the pump lost prime when the water level dropped below the skimmer entrance level, the skimmer basket is still full of water. I’ll check if I have a swivel cuff. What is a vac nipple?
 
Alright, the situation is under control now, although I couldn’t reprime the pump. You were right: the seal between the vac hose cuff and the skimmer hole is not vacuum tight at all. It wasn’t designed to be for some reason. Moreover, there’s a step down in the diameter after about one inch down. I didn’t have a vac nipple so I tried to wrap the cuff with Teflon tape and get a good seal. I did get a seal but I couldn’t prime the pump. This was OK because I did manage to clean the pool bottom using both my robotic cleaner and a heavy duty leaf rake. I wonder, in the future, if I apply the Teflon tape to the cuff in the first place, will the connection between the skimmer hole and vac line hold the vacuum even after the water level is below the skimmer? If not I may need a vac nipple, but I have no idea what it is and where to get it. Will it fit tight into that skimmer hole with the stepped down ID?
 
If you have a standard Sylvan skimmer--or almost any other skimmer, for that matter--the suction hole is threaded. Mine is a 2" thread, but 1 1/2" is pretty common, too. Any pool store should have a nipple that will fit that thread and then accepts a 1 1/2" pool hose cuff which is just pushed on to the nipple. You can get a barbed fitting at a plumbing supply store, and I have used them in a pinch. The pool vacuum nipples are smooth, slightly tapered with no barb. Here a link to one I found for sale on the net:
http://splashpoolparts.com/tapered-hose-adaptor-p-99.html?zenid=70acdab956bdf92ff15089bbf9abeb05

This one accepts both the standard sizes out there. Of course, you could just vacuum the pool and THEN drop the level, that's what I do. I wouldn't think Teflon tape on the cuff would do any good at all--maybe duct tape to get a tight fit.
 
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