how to clean a sand filter pool

Rob is a pool-service industry professional with over 20 years of experience.

Types of Cartridge Filters

There are several different types of cartridge filter housings. The pictures used in this article are for a basic capsule-style housing. Some may have band clamps in the center, others may have wing nuts on the top, and some even have a series of small cartridges. The cartridge cleaning procedure itself is the same.

How to Clean the Filter

On a level surface, rinse the cartridge with a good hose nozzle from top to bottom as shown in the picture. Do not use a pressure washer as this can damage the filter element. Keep rinsing from top to bottom turning the cartridge around until clean. That's it. Replace in housing and turn the pump on.

Tip: Always take note of the pressure. If it becomes higher each time you put the clean filter back in, it's a sign you may need to replace it. There are ways to get more time out of your cartridge.

Extending the Life of the Filter

The filter is made up of pleated material. Over time, the folds in the pleats can build up residue that cannot easily be removed with a rinse. If you spread apart the pleats and look in, you may see some discoloration and residue. When this occurs, you'll find that you need to clean the filter much more often than necessary.

This residue can be broken down by soaking the filter in Tri-Sodium Phosphate, available at your local pool store. I, personally, have found that using full-strength muriatic acid on the cartridge works very well.

NOTE: I only do this if I am replacing the filter and just trying to get a few more days of filtration out of it. This is NOT good for a filter. I pour the acid directly on the filter cartridge covering as much of the element as I can, leaving it to eat away at the residue for 3 or 4 minutes. The fumes can be overwhelming and it WILL damage the filter, so I don't recommend it unless you plan on replacing it very soon.

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How to Tell When Cartridge Needs Cleaning

There are a few different ways to tell when the cartridge needs to be cleaned:

A lack of good water flow is a definite indication that the cartridge is either dirty or needs to be replaced.
If you clean the cartridge as described in this article, and flow is still not what it should be, chances are it may need to be replaced.
Another indication is observation of the pressure gauge. I've seen many filters in which the pressure gauge is broken. It's a good idea to have a good working pressure gauge.

How to Read a Pressure Gauge

There actually is a reason that these are on the filters. Depending on a number of different things, your filter, when clean or new, will have a "normal" or clean pressure reading around 12 psi. Again, this may vary depending on your system. To determine this, of course, you'll need to have a new or clean filter. Once the pump is turned on and fully primed, check the pressure gauge. It should be between 10 to 15 psi. Let's say it reads 13 psi. Rule of thumb is that 10 psi higher than the normal or clean reading would indicate that the cartridge should be cleaned. In this case it would need to read around 23 psi (10 psi more than 13).

When to Get a New Filter

Although the cartridge can be cleaned, it does eventually need to be replaced. In my experience, it has always been that even after being acid washed, the filter simply does not allow water to flow through it, and the pressure builds within in 10 minutes.

This article is accurate and true to the best of the author's knowledge. Content is for informational or entertainment purposes only and does not substitute for personal counsel or professional advice in business, financial, legal, or technical matters.

Questions & Answers

Question: Is there a top and bottom to a cartridge pool filter?

Answer: Yes. Most cartridges indicate "TOP" or "BOTTOM"