Filters and Circulation
What is the difference between cartridge, sand and diatomaceous earth
(DE) filters?

The efficiency of a pool filter is rated by how many microns or dirt particles it
can remove from the water. If the filtration area is maximized-meaning that
you can go longer periods of time between filter cleans-and your system is
designed for maximum pumping power, your pool water will turn over faster
and more efficiently. Cartridge filters use a thick paper cartridge to filter
bacteria. Sand filters use sand and DE filters use diatomaceous earth (or a
similar product) to filter out or catch the bacteria.
Generally, cartridge filters filter out fewer microns than sand, and DE filters filter out microns
than both cartridge and sand filters. When water chemistry is properly maintained all three
filters can give you crystal clear sparkling water, but DE filters will do it more easily.
Cartridge filters have to be broken apart for frequent cleaning, where sand and DE filters can
be backwashed. DE filters have to be recharged after backwashing but sand filters do not.
Sand filters need to have the sand changed every few years to maintain their efficiency, and a
DE filter has to be torn down and cleaned at least annually. Backwashing a filter takes out
some of the bacteria, but a lot of it still remains.
In my opinion, and I think that 9 out of 10 pool service technicians will agree with me, DE
filters are the best on the market.

When do you clean filters?

Generally in the spring time ready for the summer stampede of bacteria. But in some
situations, it may be a good idea to clean the filter again after the summer to clean out the
bacteria that has accumulated from the summer past. Although this is not imperative, it is
advisable.  By keeping your pool filter in tip top shape, you are extending the life of the
elements inside that filter, which again refers to preventative maintenance.
If your filter pressure is 7-10 PSI higher than its working pressure, we would first backwash it
to see if the filter pressure reduces and remains. If it does then fine, a backwash will do.
However, if it continues to rise, the pool filter is dirty and needs to be torn apart and
cleaned.
We always backwash your pool filters regularly as part of your service. This helps to keep the
flow at its best, and also keeps the elements free and clear.

My neighbor has his pool filter cleaned like four times a year. Is this necessary and if so
why?

It really depends on what type of filter your neighbor has and how well it is being cleaned. A
cartridge filter (paper) needs to be cleaned more often because it cannot handle the bacteria.
A DE filter only has to be cleaned once or twice a year if it is done correctly. The filter
is your pools septic tank. It needs to be cleaned on a regular basis.

How long should a system circulate each day?

Many times we arrive to service customers’ pools only to find that the time clock on the pool
equipment has had the time reduced lessening the filtration. This can be a costly mistake
especially in the summer months. Filtering time is one of the most important factors
in keeping your pool water clear. Sanitation chemicals kill the water borne bacteria then it is
up to the filter to take the bacteria out. In order to do that the whole body of water has to be
sent through the filter. The pump and motor drive the water through the filter.
To calculate filtering time it is best to first find the pool gallonage. In a rectangular pool it is the
Length X Width X Average Depth X 7.5.
An oval pool is Long Diameter X Short Diameter X Average Depth X 5.9. A circular pool is
Diameter X Diameter X Average Depth X 5.9.
Next we need to find how many gallons per minute your pump and motor will move the water,
older pumps are not as efficient as the more modern ones. This can be checked by a simple
water flow meter. Finally, divide the total gallonage by the GPM, which will give you the total
amount of minutes to completely change the water. For example: Let’s suppose your pool is
30,000 gallons and your pump pumps 35 gallons of water per minute. It will take 14.5 hours
for the entire water to pass through the filter.
As a rule of thumb, we like to advise our customers to run their system 4-6 hours daily in the
winter, 6-8 hours in the spring, and 8-12 hours in the heat of the summer months.

I have had it with my filter, what type of filters do you sell?

We have a great selection of pool filters in our store. We also offer installation in the San
Diego County area.
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