How Do I Fix Low Skimmer Suction?

by Ian

I have a 4 by 8 pool depth around 4.75 and I am having problems getting a good suction from the skimmer, which I need to use the brush suction cleaner.

I have dis-mantled the pump and cleaned out the rotating fins, which were quite clean. The pre-filter is also clean.

Do you have any suggestions to increase the suction pressure?

Thanking you in anticipation.

Thanks for the question Ian

There are a few things you can check. Some are easy fixes and some may take some time to fix:

Be sure the water level is between 1/3 - 1/2 up from the bottom of the skimmer. Water level below the skimmer and your system will draw in air.

Check the pressure gauge. High pressure means a clog somewhere or a blocked filter. Low pressure means a suction side blockage, an air leak, or pump problem.

If air bubbles are coming out of the returns, it could be a suction side issue. One of the more common places for this to happen is the pump lid.

Be sure it's seated correctly and the gasket is in good shape.

If you have a weir for the skimmer, be sure it's working properly.

Skimmer basket should be clean.

Clogged pump motor impeller.

Pump motor basket needs cleaning.

Your question didn't mention the kind of filter you have. Be sure your filter is cleaned and/or backwashed.

If it's a sand filter, it may need to be degreased.

Be sure all valves are in correct positions.

Close (only temporarily) all valves except the skimmer valve. If you have no suction, the line might be clogged.

At this point you may want to call a professional pool tech to unclog the line.

Hope this helps and have a great swimming season.


Follow Up Comment:

By: Ian
Date: June 1, 2011

Good morning Robert,

Many thanks for answering my query.

Yes it is a Sand Filter. Yesterday I had the top off the filter. The sand was soft with quite a few bits of insects etc on the top.

As we are coming to the season I fitted a S Type Shower hose on to the centre return, you know, to give the splash type effect.

I noticed the pressure on the return is well down on last year. I was interested in your comment on the de-greasing of the sand.

Would this have an effect on the pressures? The pressure gauge is showing just below the green level. There seems to be no air problems, ie, air coming out of the returns, or in the pre-pump filter.

The system is around 7 years old.

Would you feel I should be changing the sand? And would this be, or could it have, an effect on the pressures?

Once again, thank you for your reply.

On another point, I was very interested on your calcium comments, and the effects on the pool grouting.

I have another pool just 7 miles away which has a different water supply and I have had the grouting gong very soft and falling out.

I thought it was a poor materials problem, however reading your comments, I have changed my mind.

Wishing you and your family all the best.

And once again thanking you for your help.

Kind regards,


Follow Up Comment:

By: Robert
Date: June 1, 2011

Yes, it could be time to degrease or change out the sand. Normally when you need to degrease the pressure is higher because the pump is being forced to work harder to push the water through the sand.

An easy was to find if your filter needs to be degreased is to take the filter lid off and feel around the inside sides of the filter.

If there are any holes, pits, edges, or if the sand clumps in your hand like sandy lard or Crisco, it's time to degrease.

A good degreaser is called GLB Filter Fresh. I've used it for the YMCA pool sand filters many times and it works nicely.

If you need to do this, just email back and I'll tell you an easy to go about doing this.

Sand normally last about 5 - 10 years, with good maintenance.

You're right in the middle with 7 years, so there may be a chance that you need to change out the sand.

If it does need degreasing, I'd change the sand out anyway because you're only going to get about another year or so until you need to change the sand anyway.

Might as well do it now and not spend extra on Filter Fresh, then turn around and spend more on sand next year.

Concerning the calcium, any time you have grouting or a plaster pool, the calcium hardness should be kept between 150 - 250ppm.

Water is hungry for calcium and will take it from anywhere it can get it. That's why with a plaster pool it's so important to keep the calcium in range so the water won't eat away at the grouting or plaster.

The water actually will pull chunks of plaster out and you'll need to do expensive repairs later on.

Even if you have a smaller pool with tile, it's important.

At the YMCA, we have a 1,000 gallon hot tub that is completely tiled, but I keep the calcium within that range.

Glad to hear from you again and have a wonderful Summer.


Follow Up Comment:

By: Ian
Date: June 2, 2011

Hello Robert,

Many thanks for your reply again.

I do like your simple answer's and to the point.

I did further investigations yesterday. I am now convinced that both the return and flow are at low pressure ie, negative and positive.

I have dismantled the pump, quite a few times, cleaned inside, however, hardly anything inside.

I have run the the system on re-circulation, ie, isolating the filter, still has no pressure so in my mind it still comes down to the pump.

It's running quite warm.

The gauge pressure reads 0.5 when the selector is on filter.

Going back to the sand, it is very grainy and not as you describe, so I feel its OK.

A point to note, when I clean the pool over the last 12 months, I always attach the hose to the head of the cleaner, then place the other end over one of the return outlets which then pushes out all the air in the hose

Before I connect it to the skimmer which I use to vacuum. Well, there is not enough pressure to blow out the air in the hose.

Hope you don't mind me picking your brains all the time.

Kind regards, and Best wishes,


Follow Up Comment:

By: Robert
Date: June 2, 2011

Sorry it's been so long to get back to you. Summer is here. Lots of questions to be answered on the website, not to mention gearing up for everything the Y is doing, and calls from customers.

Try to clean the skimmer basket(s) and pump basket to see what happens. Check the suction line to make sure nothing is blocking that.

Be sure the valves to the skimmer and bottom drain are fully open.

I don't think it was said whether you have an inground or above ground pool.

If you think the gauge is bad, there's an easy way to find out.

Turn the pump off. If the gauge drops to zero, it's good. If the needle sticks, it's bad, so replace it.

Can any air be seen in the pump motor pot? You may not have a good seal or prime in the motor.

Check the gasket around the pump lid and replace it if it's worn or damaged.

Also check the diffuser in the pump motor. This is the part that sits next to the impeller.

These tend to warp and/or melt with high heat.

You can try to narrow it down. If it is an inground pool, close the bottom drain and open the skimmer valve all the way.

If you lose pressure, the problem is with the skimmer.

Do the opposite. Close the skimmer and open the bottom drain. If you lose prime in the pump motor, the problem is with the drain.

What we've been discussing are pretty much the basics.

Anything else and you might need to call a qualified pool tech to take a look at it.

Hope this helps and let me know how it turns out for you.


Follow Up Comment

By: Ian
Date: June 7, 2011

Many thanks for all your suggestions.

It's nice just have someone hold your hand. I'm pleased to say that the problem has been cured.

The main problem with our installation is that both the return and flow pipework to the pool are a bit up and down, and easily to get air traps, and this is what the problem was.

Having turned off all the isolating valves, I removed the lid on the filter basket to the pump, then slowly opened the return pipework valve allowing the basket holder to fill up with water.

Then I switched the sector valve to filter and bleed the filter of air, at the same time replaced the lid to the filter basket.

I then opened the remaining valves still bleeding the filter of air.

On switching on I still got the pressure at 0.5 around 7psi, however, the pressure at the pool seemed greater to the feel, plus the suction on the skimmer had much improved.

You may also remember that we had had a Spa shower on the return of the pool. I have now removed this and put back the nozzle.

This has brought up the pressure to 10 psi, which has really improved the ripple effect on the top of the pool.

After cleaning the pool, a few days ago, the whole pool now seems a lot cleaner and brighter.

I think I told you I normally clean from the skimmer, but before connecting, place the hose over one of the return nozzles to blow out the air in the hose, this is now happening a lot easier.

The company who installed the pipework, in my opinion, did not really appreciate the air trap problems, as it could have been installed a lot easier, as its all in a cellar below the pool terrace.

Many thanks for your suggestions.

They did really help me in my problem solving.

Indeed I am a lot more aware of the possible system problems.

I have to get more knowledge on the calcium problem, as we do have another pool in the campo.

It does appear to be eating the grouting, which in turn holds a little algae, but not too serious.

Once again, Robert thanks for your help, very much appreciated.

Kind regards,


Comments for How Do I Fix Low Skimmer Suction?

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Help. Skimmer Does Not Have Sufficient Suction
by: Debi

My Skimmer does not seem to have sufficient suction to run my pool cleaner. It is not a sand filter and yesterday we removed the top to clean the filter. This is a new pump also about 6 months maybe. We put back the filter and closed the filter as usual . The pressure is at 10 but it is not moving my cleaner. Checked and no problem with the pool cleaner and it is apparent the the suction is not sufficient to run it. Anything else I can do.

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