What Is a Pool Skimmer and What Does It Do?

There are many parts of a swimming pool to understand when you first get one in order that you can learn to keep it clean and in good working order. A pool skimmer is one of them and it works in the following way.

A pool skimmer creates a current on the surface of a pool which draws in any floating surface debris such as leaves, oils, sunscreen etc through the skimmer opening. Any leaves and larger debris are held in the skimmer basket which stops them from reaching the pool pump. The skimmer basket can be removed and emptied.

Skimmers look rather simple, and in many ways they are, but there are a few things to consider with them.

What is a pool skimmer?

A swimming pool needs to draw in pool water from somewhere in order to send it around the filter system to clear out any dirt and keep the water clean. In most pools, this takes place within the pool skimmer.

What is a skimmer in a pool? A pool skimmer is a crucial component of a swimming pool’s filtration system, designed to remove debris from the water’s surface before it sinks or is drawn into the main filter.

What does a pool skimmer do? Typically installed in the side of a pool, the skimmer functions as a flow-through device with a hinged flap, known as the weir, at its front. As water flows into the skimmer, the weir adjusts to the flow rate, ensuring a steady intake of water and floating debris such as leaves, grass, bugs, and other contaminants.

Inside the skimmer, a collection basket traps the larger debris, allowing only water to flow through to the pool’s filtration system. Regularly emptying and cleaning this basket is essential to maintain efficient pool filtration and reduce strain on the pool pump.

How does a pool skimmer work?

The pool pump sucks water into the skimmer from the pool. The water enters the skimmer, via the skimmer door, and passes through the skimmer basket which traps any large pieces of debris to prevent the pool pump from becoming clogged.

The pool water then travels down the pipes at the bottom to the pump and through the pool’s circulation system.

Because it is located in the swimming pool wall by the surface of the pool it sets up a current that also draws in any floating debris such as leaves, insects etc. It then traps whatever it draws in and holds it in the skimmer basket for removal. The skimmer basket allows water to flow through it and into the pool’s filtration system but not any larger pieces of debris which may clog up the pool pump.

Trapping the leaves before they have a chance to sink to the bottom of the swimming pool will save you many hours of work and help to keep the pool clean.

How does a pool skimmer door work?

The best way to think of a skimmer door is that it is like a weir.

It allows a small amount of water and any floating material to pass over the top of it and enter the skimmer, but without allowing it to flow back out again.

The door is hinged and has a float material near the top which keeps it at the right level even when the water level changes in the pool and also when waves or ripples are created by swimming.

If the door wasn’t there the water would flow in still but the leaves and other debris would float out, particularly when the pool pump was shut off.

How to clean a pool skimmer?

As a pool owner it is important to clean the pool skimmer, and particularly the skimmer basket, or baskets if you have more than one skimmer, frequently. This is particularly true if there are lots of trees and other vegetation close to the pool and in autumn when the trees are shedding their leaves it is vital.

If the skimmer basket is allowed to become full and clogged by leaves and other debris then the pump will not be able to draw in water so easily and the filtering process will become less efficient.

It is better to turn off the pump before you remove the skimmer basket to empty and clean it. If you don’t then any leaves that are on the surface of the pool may get sucked straight into the system while you are emptying the basket and won’t be captured in the basket (obviously because you have it in your hand).

Knock out the larger leaves and debris from the basket, ideally into a trash bag or at the very least somewhere which won’t allow the leaves to blow back into the pool once they have dried.

Use a hose if necessary to wash out the smaller particles. Frankly, it doesn’t need to be completely spotless.

One of my neighbors has a tree that, for 4-6 weeks every year, in peak swimming season, drops very fine orange particles that blow into my pool. These do not sink but float so when they get into the skimmer they don’t get trapped by the basket they just sit on the surface.

To get rid of them I have a small fine net that came from a child’s fishing game. It fits just right in the skimmer so ideal for straining all of these particles. How I would love to chop that tree down!

Don’t forget to also check the pump strainer basket regularly and empty it when necessary. See my post How to empty a pool pump basket.

Should pool skimmers be on all the time?

Swimming pool skimmers should be on and working whenever the pool pump is on. But the pump does not normally run for 24 hours a day as this would give a large electricity bill and also cause the pump to wear out quicker.

The exception to this may be while you are vacuuming the pool through a separate vacuuming inlet and you may want as much suction as possible. So you might shut off the skimmers to achieve this as all the suction will be directed to the vacuuming inlet.

If you plug your vacuum hose into one of the skimmer inlets then obviously you cannot shut off the skimmers. To increase the suction I push a tennis ball into the remaining inlets which get held in place by the pump suction and increase the flow in the vacuum.

How many skimmers does a pool need?

This depends on the size, and to some extent, the shape of the pool. Most small to medium size pools will have either one or two skimmers. These are normally located at one end of the pool and at the opposite end to where the water enters the pool after passing through the filter system.

The reason for them being at opposite ends is that it helps to set up a current within the pool, moving the water from one end toward the skimmers.

The general rule of thumb is that there should be one skimmer for every 350-400 square feet of pool surface area. If you have too many skimmers then that may reduce the suction that each skimmer has and so they may not work effectively. If you have too few then not all of the floating debris may be captured in the skimmer.

Why are there 2 holes in my pool skimmer?

I have two skimmers in my pool. One, the furthest away from the pool pump, has only one opening at the bottom (it actually has two but one is blocked). The other skimmer has two holes at the bottom.

In that skimmer, the rear one (furthest from the pool) draws in the pool water from the skimmer, just as the one in the other skimmer does, and is where I plug in my vacuum hose.

The opening at the front is there in case the pool level drops below the level of the skimmer. If that happens then water is drawn from the bottom main drain. The reason for this is to stop the pump from running dry which may damage the pump.

Should I put chlorine tablets in my pool skimmer?

If you use chlorine tablets or one of the “all-in-one” tablets, then putting chlorine tablets in the skimmer basket is the best place. They will slowly dissolve and the treated water will be distributed around the pool by the pump. This way you won’t get a build-up of strong chlorine which could damage your pool liner (if your pool is this type).

Pool owners should never just throw the tablets in the pool as they will settle on the bottom and will bleach the color from the pool liner.

As an alternative you can use a floating chlorine dispenser that will travel around the pool slowly distributing the chlorine as the tablets dissolve. As I often have my pool solar cover on I do not use these.

Skimmer problems

If your skimmer is not skimming and water isn’t being drawn into the skimmer there are a number of possible reasons.

1. Check that the multiport filter valve is set to filter and the pump is on
2. Make sure that the valve from the skimmers is open and not closed
3. Check that the skimmer basket is not clogged with leaves and other debris
4. If all of the above is ok then it may be that the filter is clogged and not creating sufficient suction to draw in the water from the skimmer. Backwash the filter if you have a sand or DE filter or remove and clean if you have a cartridge filter. Read my guide “How to backwash a pool – step by step“
5. If none of these work then there may be a problem in the pipework. Perhaps there is a blockage caused by debris or possibly, as was the case with one of my skimmers, that the flexible pipe connecting the skimmer to the pump had collapsed preventing water flow. (I replaced it with rigid pvc pipe.)

Read my article “Why is my skimmer not skimming?” for full details.

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