Types of Swimming Pool Filter

   Swimming pool filters are the component that actually clean the water, removing small particles as water is pushed through it by the pump. Of course, if there is no water flow, there is no filtration. There are three main types of swimming pool filters:  Sand filters, Cartridge filters, and Diatomaceous Earth filters.  There are many variables, so it is important to know what type of filter you have before any attempt to repair it.  Different filter designs and materials mean a variety of greatly different potential repair issues, so the best tool you have is the owner's manual.  It is important to know how the filter works, in order to know when something is wrong.  Often, the filter gets "blamed" for working improperly, when, actually, there is a chemical or other problem with the pool.  Filters are fairly simple, and usually, when properly maintained, are trouble free for many years.   Here, we'll give you a quick overview of the different types of swimming pool filters,  and how they work.

Sand Filters

   Sand filters are the most common type of pool filter in Oklahoma, and generally, the easiest to maintain.  Most have a control valve, either on the top, or mounted to the side, which controls the flow of water through the filter media, and where it goes when it leaves. 

   In the filter position, water enters the top of the filter through a diffuser, which keeps the water from boring a hole in the sand.  The sand is what actually filters the water.  There is an under-drain, in the bottom of the tank, effectively, a screen, that keeps the sand from running through the standpipe, and back to the pool.  The sand, in turn, filters out the smaller particles, which, in turn, filter out even smaller particles.  A sand filter is actually doing it's finest filtration when it is dirty.  As the filter gets dirty, pressure builds up in the tank, until the pump begins having a hard time pushing water through it at at all.  At some point before this happens, it is time to clean the filter.  A sand filter is cleaned by backwashing.  To backwash the filter, turn off the pump before moving the handle between positions.  Push down on the control valve handle, and rotate it to the backwash position.  Usually, this is 180 degrees, or opposite, from the filter position.  In the backwash position, water runs backwards through the filter - down the stand pipe and up through the sand - and out through the waste port.  Since the sand is fairly heavy, it stays in place, and the finer particles that have been removed from the pool water are washed out the waste port.  It it can waste a lot of water to thoroughly clean the sand, and that isn't even necessarily desirable.  But if you go directly back to the filter position, a lot of small particles will go through the unsettled sand and back to the pool.   To prevent this, there is a position called Rinse or Filter to Waste.  It is usually the first position before filter when rotating the valve clockwise.  In this position, the water runs down through the sand, up the standpipe, and out the waste pipe.  This resettles the sand base.  Run the filter in this position until the water in the sight glass runs clear.  Now only clear, filtered water runs back to the pool, and the cycle begins again.  In the Recirculate  position, water never actually enters the sand filter, but is diverted directly back to the pool.  This position is used when using flocking agents, or other chemicals that need to be added to the pool without clogging the sand.  The Waste position is usually the first position before Backwash. It  sends water directly out the waste port, without going through the sand.  This position is used when vacuuming up algae, which is so fine that it would go right through the filter.  It is also used during spring cleanup, of whenever you need to lower the water level in the pool.  The  Closed  position keeps water from running through the valve, and is seldom used.

   With sand filters, it is good to lubricate the o-ring on the valve distributor shaft every year or two, but other than that, they are best left alone.

Diatomaceous Earth Filters

   Diatomaceous Earth filters, or DE filters operate pretty much the same as sand filters, except that instead of sand and an under drain,  they use filter grids and a powder called DE.  Unlike sand filters, the filter media is lost while backwashing, and has to be replaced each time, with a specified amount of powder.  The up side is that, even when clean, the DE filter will filter out very fine particles, like a sand filter does when it is dirty.  the down side is that you have to buy the powder, and it is kind of messy.  Be careful not to breathe it, because it has jagged edges, and can harm your lungs.  The way you get the DE into the filter is to add it through the skimmer with the pump running.

   DE filters are a little more delicate than sand filters, and require more care.  The filter needs to be taken apart at least yearly, and the filter grids need to be deep cleaned using an acid or alkaline cleaner.  The grids can be torn or come unsown, so inspect them for holes.

Cartridge Filters

   Cartridge filters are not as efficient as DE filters, but they produce no waste.  The cartridges are taken out and washed, then reused.  Eventually, they wear out, and have to be replace

Common Filter Repair Issues

Dirty Water Returning to the Pool

   One of the most common filter repair calls we've gotten over the years is that dirty water is going back to the pool.  Usually, these calls com in during spring cleanup, when people are vacuuming up algae.  They have cleaned the filter really well, or backwashed thoroughly, and still, stuff just keeps going right through the filter.

   Well, first off, if you have algae, it will go right through the filter, especially a clean sand filter.  Your initial spring cleanup should be done in the waste position.  A clean sand filter is designed to take out particles down to about 30 microns - much larger than algae.  so, during spring cleanup, vacuum to waste, then chemically treat the pool, and be patient.  Some people use clarifiers, but I don't recommend them.  just let the filter get a little dirty, and it will start to filter out the smaller particles.  DE filters take out much smaller particles than sand filters, but you may still see some algae that goes right through.  As the filter gets dirtier, almost nothing gets through.  The problem with that is, you have to keep changing out the filter media.  Again, vacuum to waste during spring cleanup.  When you first coat a DE filter, it is normal for a small amount of DE dust to go back to the pool.  Once the filter grids are fully coated, almost nothing gets through (the spec -s 3-5 microns).  If you appear to have a lot of DE going back to the pool, you may have hole in a filter grid, cracked manifold, or a control valve that needs repair.  Clean cartridge filters are rated at about 16-20 microns, so just about all algae, and some larger particles will go through them.  Some people coat the cartridges with a small amount of DE to make them more efficient. Often, the builder fails to provide a way to vacuum to waste with cartridge filters, so if this is the case with your pool, call your builder up and smack him in the face with a wet beanbag chair, then install a waste valve.

Losing Water Through The Waste Line

   Water loosing water through the waste port is a problem in the control valve.  The best preventative measure you can take is to service the valve once per year.  Take the top off, inspect the valve body, and replace the spoke gasket if it needs it.  Take the handle off, slide the distributor assemble out of the top of the valve, clean it, and lubricate the o-ring.  Other than the spring getting weak (not likely) that is about all that can cause the valve to bypass.  If the valve handle is "crickety" and hart to turn, it is a good sign that the distributor shaft o-ring needs to be lubricated or replaced.  Also, check the Teflon bearing that is directly under the handle.  It is the (white) disc that the handle leverages against when you push the handle down to turn it.  If this bearing is absent or worn out, the distributor will not come up enough to clear the 5 spoke gasket, and will damage it when the valve is rotated.  This leads to - yep, you guessed it - water leakage through the waste line.

Changing Sand in a Sand Filter

   Personally, I think a lot of money is wasted each year by unnecessarily changing sand.  Pool stores and even manufacturers recommend changing sand after somewhere between 1 and 5 years.  Of course they do.  They want to sell parts.  Because of the likely hood of breakig the under drain and other parts, I lean more toward "If it ain't broke, don't fix it" approach when it comes to changing sand.

    Since the "when and why" is covered elsewhere, lets discuss the  the "how".  Turn off the power to the pump.  If your control valve is on the top of the filter, remove it.  (You may have to cut some pipes - another good reason to leave it alone.)  If your control valve is mounted on the side of the filter, remove the top access panel and the diffuser. 

   There are several ways to get the old sand out.  Dipping it out with a cup is a long, slow process, and you will probably scrape your arm.  Tipping the filter over to dump the sand out is a good way to break the underdrain or standpipe.  You can do it with a shop-vac, but you'll have to dump it a few times, and you need to have the internal filtration in place to protect the motor.  Some pool stores sell a sand vac, which is pretty handy, basically a funnel with a jet inside that attaches to a garden hose.  Water gets forced  out through a discharge hose attached to the small end of the funnel, taking sand with it.

   A few years back, I came up with a pretty easy and inexpensive way to remove sand from a filter.  I use a siphon hose.  1" or 1 1/4" hose works pretty well, about 10 feet long.  Fill the  filter with water, and leave the water running into  the filter.  Submerge the siphon hose under water to get all the air out, thee cap one end with your hand, and quickly lay the end on the ground to start the siphon.  Simply vacuum the sand out.  If the hose clogs, you're trying to take too much sand at one time.  Usually, if the sand  is not contaminated by high chlorine levels or algaecides, you can spread it out in flower beds or elsewhere in the yard to dispose of it. 

   When you add the new sand, use exactly the specified amount of the correct filter media.  It is not just river sand, is is of a specific size and grade.  Don't breathe the dust.  Before adding sand, cover the standpipe to prevent dumping sand down it.  Add some water to the tank to cushion the underdrain assembly, and add the sand slowly.  Once you have put all the sand in, lubricate all the o-rings you encounter, and reassemble the filter.  If you had to cut plumbing to take the valve off, it is a good idea to replace the o-ring between the tank and valve. It's a bummer to have to cut PVC twice if the old o-ring leaks.  On top mounted valves, there is also an o-ring that should be lubricated on the inside of the diffuser, where the standpipe goes in.

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 Pool Filter Repair Oklahoma City Edmond Moore Mustang Yukon

   A-Pro Services, Your Pool and Spa Service Company, repairs swimming pools, spas, and hot tubs in the Oklahoma City area, including OKC Edmond Yukon Mustang Moore

   A-Pro Services, Your Pool and Spa Service Company, repairs swimming pools, spas, and hot tubs in the Oklahoma City area, including OKC Edmond Yukon Mustang Moore

   This page about filter repair on PoolRepairOKC.com  is presented from the repairman's point of view, to explain different types of filters, how pool filters work.  While I can't explain everything on this page, maybe I can help by at least explaining a few things to check before you pay a repairman.   We hope you enjoy this site, and find it useful!

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