How To Troubleshoot A Pool Pump That Is Not Full Of Water


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When working correctly, pool pumps should be completely full of water. In this guide, we discuss different tips on how to diagnose and correct the issue of a pump that is not filling up all the way.

Note: This guide is meant for pool owners who are used to seeing a full pump and a half-empty pump is out of the norm. There are instances where a variable speed running on a low speed will not fill up the pump completely. This is ok as long as the water level does not continue to fall and cause the pump to run dry.


Step by Step


Step 1

CHECK VALVES - The first thing to check is the valves on the suction side of the pump. They may have been turned inadvertently, causing a decrease in flow to the pump.

The skimmer lines and main drain lines should be open.

Step 2

WATER LEVEL - The water level of the pool should be at least halfway up the skimmer door opening. A low water level could create a situation where the pump runs half empty or dry.

Step 3

WEIR DOOR - The pool skimmer weir door can get stuck in the upwards position. This would cause a decrease in flow. Make sure the weir door can swing back and forth.

Step 4

SKIMMER BASKET - Check the skimmer basket and clean it out if necessary.

Step 5

PUMP BASKET - With the pump off, check the pump basket and clean it out if necessary.

Step 6

PUMP LID O-RING - The pump lid o-ring seals the lid so that air can't get in. Try lubricating the o-ring with a teflon or silicone lubricant. Replace the o-ring if it is stretched out or cracked.

Note: This solved the issue in the video posted above.

Step 7

SUCTION SIDE AIR LEAK - The pipes and valves before the pump can be sources of an air leak. An air leak will cause the pump not to fully prime. 

Check out our blog titled "How to Find Suction Side Air Leaks".

Step 8

CLOGGED LINE - A clog in a suction line can hamper the ability of the pump to fill up with water. This usually happens if debris is manually vacuumed directly into the skimmer line. A vac plate or leaf canister should always be used.

Feeding an electrician's fish tape down the lines will sometimes free up a clog. You can also try using a plumbing bladder on the end of a hose.

Step 9

CLOGGED IMPELLER - Fine debris can bypass the baskets and clog the impeller. The impeller can not pull enough water if it is clogged. 

You can try unclogging the impeller with a wire hanger. If that is not possible, the pump will need to be taken apart in order to access the impeller.

Check out our guide titled "How to Clean Out a Pool Pump Impeller".

Step 10

TRY PRIMING AGAIN - If all else fails, try to manually prime the pump with water. After filling up the pump with water, turn it on and let it run full speed for several minutes.

Check out our blog titled "How to Prime a Pool Pump".


(1 to 7 of 7)

 Posted: 8/23/2022 

Thanks so much, problem solved

 Posted: 6/25/2022 

Your website is really helpful! Thank you for all the great pool care and maintenance tips. I'm getting air in my pump so tried some of these troubleshooting techniques today. When I try to manually prime the pump by filling it with water from a hose, I cannot get the pump to fill up. I have 3 lines coming into the pump - 2 from skimmers and one from the main drain. I tried closing valves to from the different locations to fill up one line at a time, but could never get the lines or the pump to fill up. Any ideas on what I could try next, short of having a professional help? Thanks!

InyoPools Product Specialist  Posted: 6/27/2022 

How long do you let the hose run for? is the pool's water level midway up the skimmer?

 Posted: 3/12/2022 

I lost all water to just below intake and output lines on above ground pool due to a break in the pump basket. I replaced the basket and o-ring but the pump will not allow water to go in when refilling pool. As soon as level reaches line in pool, the water comes out the top of pump backwash line. Pump has not been run since water drained out.

InyoPools Product Specialist  Posted: 3/14/2022 

The multiport valve either needs to be adjusted to regular filtering mode or has a crack/leak in it. Water wouldn't be pouring out of the backwash line unless it was being incorrectly routed. More info can be found here: Why Is My Multiport Valve Leaking?

 Posted: 6/27/2022 

I had the same thing. The spider gasket in the multiport valve needs replacing. I inspect mine and it was all deteriorated. While you are there replace the o-rings as well. They kits online

InyoPools Product Specialist  Posted: 6/27/2022 

The gasket kits are found on the valve's parts schematic, listed on this page: Filter Valve Parts