What Happens When You Don’t Backwash Your Pool?

Proper filtration of your pool water is essential, not only to the appearance of your pool but also to the health and safety of your swimmers. Having said that, what will actually happen if you simply don’t backwash your pool?

  • Increased water pressure strains the pump, eventually damaging it.
  • Water can’t travel freely through the sand, so your system will experience reduced flow, rendering your pool cleaner useless.
  • Your pump can lose prime and run dry
  • The filter will no longer be able to remove dirt from the water.

Neglecting the backwashing of your pool filter is not a good idea you lazy bugger. It could cost you a ton of money in repairs or replacements. Let me explain in more detail why you should be backwashing regularly.

Increased Water Pressure

As your filter cleans the pool water, it traps dirt particles in the sand inside the filter. After an extended period of time, these particles of dirt, grime, algae, etc. will block up the sand in the filter. This will make it difficult for the water to pass through.

Now, the line leading from the pool to the pump is under a lot of pressure, this, in turn, puts the pump under a lot of strain. If your filter has a pressure gauge, you will notice that the pressure is abnormally high when the filter dirty and it is due to be back washed.

If you leave the system to run in this condition, you may damage your pump.

Other reasons for increased water pressure:
There are also other causes of increased water pressure. Here are some causes I found at the site Inyopools.com

  • Certain blockages in the outlet (after the pump and filter), can cause a bottleneck, increasing the pressure inside the filter.
  • Having too many turns in the plumbing can also increase the pressure as each turn adds friction and pressure to the system. All plumbing should have as few turns as possible.
  • Your pump might be too large or powerful for your size of the filter.

Unable to filter pool water

The tiny bit of water that manages to pass through the filter by now, will be pushed through tiny little channels formed in the solid mass of sand and grime. These little channels are not able to trap any dirt inside the filter, and end up right back where they started, in your pool!

Other reasons why your filter may not be cleaning properly:
Some other causes of this I found on the website intheswim.com are:

  • The pool filter is leaking water around the clamp
  • There is not enough sand inside the filter, and so the water is passing too easily through the filter without trapping any dirt.
  • The sand inside your filter is worn out. New sand is not perfectly round, as a matter of fact, the grains have jagged edges that better trap the dirt in the sand.

Reduced Flow

Now that you have neglected your backwash duty, the filter is completely blocked up and your poor pump is straining to push the water through a solid block of dirt, rather than loose sand.

Are you proud of yourself?

Because of this, the rate of flow through the system is drastically reduced. What does this mean? Well, without suction, your beloved pool cleaner is nothing but a useless pool ornament. It will not have enough flow to do anything really.

Which leads me to my next point.

Running Dry

If your pump is left to strain under pressure and with reduced flow, it may not be able to maintain enough “suction” to keep the line primed with water. And if your pump is not sucking water, it is sucking air.

Running your pump dry is extremely harmful and can damage it beyond any possibility of repair.

Read my previous article on what happens if you let your pool pump run dry.

Other reasons that may cause your pool pump to run dry:

  • Air leaks in the line from your pool to your pump.
  • The pool water level is not above the skimmer and water is being sucked into the system.
  • The skimmer basket is not clean. If water cannot pass through this basket, your pump will start sucking air instead.
  • Your pool cleaning hose may have a leak in it.


It is so easy to neglect to backwash your pool, especially when you are barely using it in the colder months. However, leaving this for too long can eventually lead to expensive damage to your pool pump.

If left for too long, your system will experience increased water pressure, putting a lot of strain on your pool pump. This increased pressure in your system is caused by the complete clogging up of the sand inside your filter.

This sand is now unable to clean any of the water that manages to channel its way through the filter at abnormally high pressures, leaving your filter useless and your pool dirty.

It doesn’t end there either.

If left for longer, your pump will not be able to generate enough flow to properly operate the pool cleaner. Now algae will start to form on your pool walls and leaves will accumulate at the bottom of your pool.

Now your pool looks disgusting and is also too unhygienic to use. Well done.

If you continue to neglect the backwashing, your pump will not be able to generate enough flow against the pressure of the blocked-up filter, and this will cause your pump to lose prime.

This means that instead of pumping water, your pump will be pumping air. This can lead to catastrophic damage to the pump itself, leading to expensive repairs, or even possible replacement!

PS. I got some water in my ear while swimming last night. The feeling is quite ear-ittating.

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