There are three popular types of pool filters in use today. They are sand, cartridge and the finest pool filters money can buy… DE Filters!
DE filters: Filter range about 1 to 3 microns. That's really small!
That's why I only install Pentair FNS Plus DE filters in 36 or 48 Square Foot sizes.
Cartridge filters: used to be cheaper to buy so pool guys would sell them often to build in more profit. Today, comparable sized DE and cart filters are about the same price for the better brands. When you are talking about the difference between DE and cart filters the biggest difference is the filtering ability or micron size. Cart filters are about 10 to 20 microns... DE filter are 1 to 3 microns. What this means to Mr. & Mrs. Pool Owner is that they may be swimming around with dirt and debris particles getting in their ears, eyes and other places without even realizing it. Why would we want them to do that? We wouldn't, so install DE filters and get crystal clear and sparkling water that everyone will notice. "My pool is sparkling like diamonds in the morning sun!"
A Morgan Quote!
Sand Filters: The oldest form of pool filter. Filter range about 20 to 40 microns. In my view, use them in large volume applications such as Jr. Olympic and Olympic sized pools. That's all for sand filters. How do they work? Water is pushed through a bed of filter sand and removed through a set of lateral tubes at the bottom. The filter area of a sand filter is equal to the area of the filter itself. For example, a 24" filter will have 3.14 sqft of filter area. Only the top 1" of sand is actually used to filter the water. The principle behind this filter is that water is pushed through the filter sand, somewhat like an espresso machine. Dirty water goes in the top and clean water exits out the bottom. As the filter sand becomes plugged with debris from the pool, the pressure increases on the filter and the water flow drops. In order to clean the filter, you just run it in reverse and dump the waste water; this is referred to as "backwashing" the filter. Once the filter is backwashed, you move to the rinse mode and that repacks the sand and then back to filter. This has to be done manually every few weeks. From a hydraulics standpoint, a backwash valve is typically the most inefficient piece of equipment you can add to a swimming pool system. Should the sand ever become really dirty, it may be replaced. Now there's a fun job!!! In terms of particle size filtered out, sand is the least effective method.
Filter Operations:
Cart Filters need servicing more often that DE filters because they are basically constructed of a paper product element. This element gets bunged and then needs to be pulled out and hosed down. When hosing out a cart filter element use a strong hose end gun and move the water flow up and down the veins with top to bottom motions so as to "sweep" the debris out with your water flow. Cleaning cart elements is about as much fun as listening to politicians talk! Getting a cart filter element out of the filter tank is pretty self explanatory. Getting the lid sealed back up on a cart filter tank after your done is always important. Some cart tank lid O-Rings require lube and some don't. Single element cart filters seem to do well dry but multiple cart filter tank O's always get lubed. For cart filters, little
can go wrong. The cart is usable and reasonably new or it is old and must be replaced. A new cart element is white. When it gets too old to be of much use, it will be brown and the PSI will be very high, even after you've cleaned it.
For DE filters, a degree of abuse may come into play. The elements are more technical, fragile and subject to a high degree of scrutiny during a service operation. DE filter service consists of dismantling all components of the filter found inside the tank. Then, a thorough cleaning and inspection. Getting the upper half of the DE filter tank to seat correctly is often a trade secret!
Filters/Continued:
There are four main components of DE filter guts! Grids, manifold, spreader wheel and through rods. Inspect the manifold for cracks and the grids for tears or punctures of any kind. High pressure inside the filter tank will force debris through any ruptures in grids or manifolds and return the debris right back into the pool by way of the clean water return line. The spiny plastic skeletal matter inside DE filter grids sometimes becomes old and fatigued. This caused a "crushed" grid condition. We usually replace crushed grids. We always replace ruptured grids.
The cleaned and reassembled filter element package gets fit over the stand pipe which has a small O-Ring. Carry lots of these on your truck and replace them when in doubt. The tank O on the other hand is large and can sometimes become stretched out. When this happens you'll probably have a difficult time getting the tank lid to seal correctly and will have to replace the tank O! Modern vertical grid DE filters have 8 grids. 7 full sized grids and one "partial!" This allows room for the stand pipe assembly. Reassembling a Pentair FNS DE Filter is a snap due to the smart spreader wheel format. Reassembling a Hayward vertical grid DE filter is a pain in the ass!
The best way to learn is to get your hands on a filter and just check it out!
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