Pump won't prime after halfway draining pool

tangouniform

Well-known member
Apr 12, 2014
62
Central Tx
#1
I'm in the process of draining my water level below my light to do some maintenance on it. I'm using my pool pump to drain it, taking water only from the main drain and suction side vacuum line (both skimmers are turned off via diverter valve). Everything was going fine but I decided to give my pump a break, so I turned it off. A couple hours later I turned it back on but there was no prime. I tried to manually prime the pump via water hose in the pump basket. When I turn on the pump, it'll suck in the water in the basket but nothing else, no prime. I then put a hose in one of the skimmers and opened up the diverter but no change.

So the only thing that's changed from my normal pool operation is that the water level is below the skimmers, which is why they're off via the diverter. Since the water is below the skimmers, and it won't prime, am I correct in thinking that air is probably getting in through one of the skimmers causing the lack of prime? Like I said above, everything was working fine until I turned off the pump then tried to turn it back on. Is it possible that the leak is small enough that it didn't lose prime while it was running but once I shut it off and tried to turn it back on, that it's letting enough air in to not start a prime?
 

dumbcluck

LifeTime Supporter
Aug 4, 2013
674
long beach
#2
I know this doesn't answer your question but why would you drain the pool to service the light? It's designed to pull out of the water onto the deck for such purposes.
 

duraleigh

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Apr 1, 2007
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Sebring, Florida
#4
The lowered water level has likely increased the "suction" required to pull the water from the pool water level to the pump. Your pump is simply not strong enough to lift the water that much higher.

If that's the case, I know of no easy fix. YOu don't happen to have a spigot on the pressure side of your system, do you?
 

tangouniform

Well-known member
Apr 12, 2014
62
Central Tx
#5
The lowered water level has likely increased the "suction" required to pull the water from the pool water level to the pump. Your pump is simply not strong enough to lift the water that much higher.

If that's the case, I know of no easy fix. YOu don't happen to have a spigot on the pressure side of your system, do you?
This was my fear but didn't know if it was possible. I wasn't sure how much the weight of the water itself helped pull it through the suction lines. No spigot that I know of.
 

duraleigh

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#6
I wasn't sure how much the weight of the water itself helped pull it through the suction lines.
The pump must create an area of low pressure to allow the water to be lifted up into your pipes and pump. It is pretty significant.

Pumps like to "push" water but they do not like to "suck" air.
 

mas985

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May 3, 2007
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#7
Theoretically, most residential pool pumps should be able to prime up to 8' or so but it usually requires some help like priming valves on the suction line and completely air leak free. This allows you to fully fill the pump basket with water which in turn helps develop low enough pressure in the pump basket so atmospheric pressure can push water up the pipe.

But if you are trying to empty a pool, you really shouldn't stop the pump because it is so hard to re-prime. However, even doing that doesn't guarantee that you will be able to empty a pool. As the water level drops, suction in the pump basket increases and the pump lid gaskets are more likely to leak air not to mention other parts of the plumbing so in a lot of cases, the pump will lose prime anyway.

Dave, isn't your pool that requires a high lift when priming?
 

duraleigh

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#8
Dave, isn't your pool that requires a high lift when priming?
Yes! (good memory). I have never shot it with a level but I would say it is about 6 - 6.5 feet and a real bear to prime if I lose it.
 

Soonersalt

Well-known member
Oct 6, 2013
50
Oklahoma
#9
If I was you at this point is to rent a pump w a 3 to 4 inch line and finish your job vs trying to deal w loss of prime at this point. Prob $60-$80 per day


Sent from my iPhone using Tapatalk
 

JamesW

TFP Expert
Mar 3, 2011
12,677
#10
In some cases, you can set up a siphon to drain the pool. If you have a spot lower than the level you're trying to drain to, then you could set up a siphon. You could try plugging the skimmers to see if that allows you to restart the pump. Or you could by a small submersible pump to finish the drain.