When you are vacuuming your pool you need sufficient suction to pick up all of the dirt from the bottom of the pool.
If there is not enough suction then some dirt will be left behind as you vacuum which is likely to go into suspension in the water when it is disturbed and will then resettle on the bottom again later.
In this article, I will first show how to increase the suction when everything is working correctly to improve the performance of your pool vacuum, ensuring cleaner and clearer water for your swimming pool.
Then I will show how to troubleshoot should you lose suction while vacuuming.
How to increase pool vacuum suction
It is not unusual when you plug a pool vacuum hose into the skimmer for the suction in that skimmer to reduce but increase in the other skimmer or skimmers. This may mean there is insufficient suction for the pool vacuum to work efficiently.
To increase the suction in the skimmer you are using to vacuum from there are two ways you can increase it which are:
Close skimmer/main drain valves
If you have separate valves to control the flow to each skimmer then you can close the valve to the other skimmer or skimmers which will, as a consequence, increase the suction to the skimmer that the vacuum is attached to.
Also, you can close the main drain valve if it is open to increase skimmer suction.
Using a tennis ball
If you do not have separate valves to turn off/on individual skimmers, which is the case with my pool, then you can use a tennis ball or some other relatively hard ball that is larger than the hole at the bottom of the skimmer.
With the pool pump running push the ball down into the skimmer until the suction pulls the ball into the entrance to the hole and seals it. The suction will now be significantly higher through the vacuum hose allowing you to remove all of the debris on the bottom.
WARNING: Ensure the ball is not too small or soft otherwise it may be sucked into the pipe. A tennis ball works well in my set up.
Checking for problems
If your pool pump has low suction meaning you have insufficient suction in your pool vacuum, particularly if it suddenly occurs while you are vacuuming, then make sure that there are no problems in the system by checking the following:
Variable speed pump on high
This may sound obvious, but if you have a variable speed (VS) pump then check that it is on the high setting as on the low setting it will create less suction.
A sudden reduction in suction could be as simple as a problem with your vacuum head. Check that there are no blockages in the pool vac head itself such as leaves or other large debris trapped underneath.
There are two things that may be causing reduced suction in a pool vacuum hose:
- There could be a blockage somewhere along the hose if a large number of leaves have been vacuumed up. Fortunately, with many vacuum hoses that are semi-see-through, you can see if this is the case easily.
- The hose could have a split or hole in it which could mean either air is being sucked in at a point where the hose is out of the water or it could be sucking in water if in the pool. Both would reduce the suction in the vacuum head.
Skimmer basket (if using a skimmer plate)
If you have plugged the vacuum hose directly into the skimmer then you will have removed the skimmer basket so this will not be an issue.
However, if you have the vacuum hose plugged into a skimmer plate fitted above the skimmer basket then as you vacuum leaves and other large debris will have been trapped in the basket. If this becomes too full then it will cause a reduction in the suction.
You just need to remove the basket and empty it.
I can sometimes experience a loss of suction while I am vacuuming my pool on the filter setting when the bottom of the pool is quite dirty, but not so dirty that I need to vacuum to waste.
Basically, the filter starts to get clogged meaning the pump has to work harder to push the water through the filter, the filter pressure increases and the suction reduces.
To rectify the situation I have to stop vacuuming and backwash the filter. If you are unsure how to do this then please refer to How to backwash a pool sand filter.
Pump strainer basket
Particularly if you are not vacuuming using a skimmer plate (when leaves etc will be trapped in the skimmer basket) and large debris such as leaves will pass through the skimmer pipework and be trapped in the pool strainer basket, to prevent them from clogging the pool pump.
This basket is generally quite small so can become full quite quickly and when it does it restricts the flow of water to the pump. You need to turn off the pump, remove the strainer lid and empty the basket.
If you are unsure how to do this then read my post How to empty a pool strainer basket.
Air in the filter
Air can be trapped at the top of the sand filter housing and if sufficient air accumulates there it will affect the suction.
Most sand filter housings will have an air drain valve at the top, perhaps behind the pressure gauge.
- Turn the knob anticlockwise until you either hear hissing air coming out. Continue until water starts to stream out constantly then close the valve.
- If water streams out immediately you turn the knob then there is no air in the system.
Air lock in pump
If the pool pump has an air lock then it will be unable to pull water through the skimmer/s. You should be able to tell if there is an air lock:
- the pump will make a different noise than normal
- if you look through the transparent lid of the pool pump strainer housing you should see the air in there.
In this post, you will find various ways to prime a pool pump.
You can help prevent getting an air lock when setting up your vacuum by ensuring that you remove the air from your vacuum hose before you start to vacuum.
Skimmer line blockage
If everything else appears correct then there is a possibility that you have a blockage somewhere in the line from your skimmer to the pump.
I find the best way to test this is to shut off the pool pump, take off the lid of the strainer housing and remove the basket. Then push a hose into the pump inlet and turn it on full.
If water flows out of the hole in the skimmer easily then it is unlikely there is a blockage.
However, if little or no water comes out (and actually flows back into the pump housing then you probably have a blockage that could be caused by debris or a collapsed flexible pipe (as I had a few years ago).
Hopefully, if the line is blocked with leaves and other debris, the backflow of water will clear these and whatever is blocking the line will come floating up in the skimmer.
Pool pump impeller clogged
You may have reduced suction if there is something caught in the pool pump impeller that is perhaps not fully preventing the impeller from turning (in which case you would have no water flow at all) but something smaller such as a small twig that is trapped and slowing the impeller. I have had this happen twice.
To check the impeller, in most pool pumps you can remove the strainer basket and put a finger in the hole towards the pump. You should be able to feel the impeller which should spin freely if not blocked in any way. Obviously, if you feel anything trapped then try to remove it.
Pool Maintenance Course
When I first bought my house with a swimming pool, I knew nothing about cleaning and maintaining it.
I was recommended Swim University’s Pool Care Handbook and video course so I bought it and have never regretted it.
It was without a doubt the best money I spent that year as I saved thousands by doing it myself.
What if you lose suction while vacuuming
Pool pump loses pressure when vacuuming on filter
It can often happen if you are vacuuming your pool with the multiport valve on the filter setting, particularly when the pool is quite dirty but not dirty enough to vacuum to waste.
If this happens it is likely to be one of three things:
- The most likely cause is that the filter is clogged so you should stop vacuuming. If it is a sand filter you should backwash and if it is a cartridge filter then the filter/s should be removed and cleaned.
- The pool pump strainer basket may be clogged with leaves or debris so you should clean it out to restore suction.
- If you are vacuuming using a vacuum plate, so the skimmer basket is still in place, then you may have reduced suction due to that being full and blocked.
Low suction when vacuuming to waste
If you suddenly have low suction when vacuuming to waste it is probably that the strainer basket is full and preventing sufficient water from reaching the pool pump. So turn off the pump and then empty the pump strainer basket.
If you are using a vacuum plate in the skimmer to hook up the vacuum hose then the skimmer basket may need emptying.
Why is my pool vacuum suction weak?
Pool vacuum suction can become weak for various reasons. This might be due to blockages in the hose, leaks, a dirty filter, or problems with the pool pump. Regular maintenance and cleaning can help avoid these issues.
Can a dirty filter affect my pool vacuum’s suction?
A dirty filter can significantly impact your pool vacuum’s suction. If the filter is clogged, water can’t pass through it efficiently, which reduces the suction. Cleaning or replacing your pool filter can improve suction.
What should I do if there’s air in my pool vacuum system?
Air in your pool vacuum system can cause weak suction. You can remove air by ensuring the hose is filled with water before connecting it to the skimmer. Also, check for leaks in the hose or connections as these can allow air to enter the system.
I have had hot tubs for over 20 years and a pool for the last 10 years. I had to learn how to clean, maintain and fix them the hard way. Since then I have helped many friends and neighbors with their pools and now I want to share everything I have learned with you. About Me