Pool Filters


Example of a D.E. FilterDE POOL FILTERS


The D.E. filter is the most efficient type of pool filter on the market. It can trap particles down to 3 - 5 microns; well below what the naked eye can see. DE filters, like most pool filters, use a pressure gauge toindicate a need for backwashing when it reads 8 - 10 lbs. higher than its clean reading. After backwashing a D.E. filter, a new application of D.E. filter powder is added to the filter by pouring into the skimmer. An annual breakdown of the filter is necessary to thoroughly clean D.E. filter grids.


The Powder is what does the filtering. A D.E. filter requires that the operator (you) add D.E. powder to coat the filter grids inside of the filter tank. This widely available, inexpensive powder is actually the microscopic skeletons of Diatoms, an ancient, sub aquatic creature. Under the microscope, these skeletons appear to be tiny sponges. This is where the dirt gets trapped in your filter. The powder, which is added at your skimmer, dissolves in the pipe on its way to the filter tank. When it reaches the grids, which are covered with a nylon type of fabric, the powder stops, coating the grid. DE Grids are also called Elements or Septums. The water continues to pass through, first through the powder, then the fabric covered grid. As the water passes through the D.E. and enters the grid it leaves the dirt, trapped in the D.E. powder "cake" or coating. The powder is the filter.


The D.E. powder is what filters your pool water in a D.E. filter. Do not operate your pump without having the D.E. powder coating the grids, or you will see your pressure rise very quickly, and if left in this manner the grids could become damaged. As the pressure gauge on a D.E. filter increases, flow rate decreases. Eventually the flow rate will allow the water quality to suffer. You will need to backwash the filter to remove the D.E. that is clogged up with the dirt.

After backwashing thoroughly, add new D.E. powder to the filter through the skimmer. If using biguanides (Soft Swim or Baquacil) you will need twice annual, very thorough cleaning to prevent it from gumming up. All D.E. filters should have this done at least once per year. Thorough cleaning is accomplished by turning the pump off and draining the filter. Remove the tank top half, and remove the grid assembly. Hose the grid assembly thoroughly. If you want to do an extra good job, after hosing, soak the assembly in a trash can filled with water and a filter cleaner product. (or use TSP {trisodium-phosphate} from the hardware store). Rinse thoroughly before reinstalling grids into tank.

While cleaning the DE grids, it's good to inspect them for tears and holes. Holes in your DE grids larger than 1/2 inch will need to be sewn, or replaced. Inspect also for mis aligned grids, and correct, and check that the through bolts are tightly secured so that the assembly is drawn close and the grids are snug into the top manifold and the bottom spreader plate.

When backwashing a D.E. filter, bump the filter several times. That is, backwash until water runs clear, move the multiport valve to FILTER and run it on filter for a 5 - 10 seconds, and backwash again until it runs clear, etc...do this 2 - 4 times. Remember to always shut off the pump before turning your multiport valve or your push-pull valve. Each time you go through the cycle of filter/ backwash/ filter, you will get more dirt/ D.E. out of the filter, giving you a better, more thorough backwash.

Be cautious not to pump DE waste water directly into streams as it may choke small aquatic life. Your city or town may have discharge regulations for DE powder.

If you are using a separation tank for backwashing, or a separate tank that separates the DE from the waste water, and returns clean water to the pool (prevents water wasting) - it is especially recommended to bump the filter as described above, and run your backwash cycle for a longer time period, maybe 10 minutes. Using a sep tank may also require more frequent manual cleaning of the DE grids, because the backpressure reduces the overall flowrate during backwashing.

Also important in ensuring an effective backwashing is to make sure skimmer baskets and pump baskets are clean to allow for full flow entering the filter.


How do I Backwash my DE Filter?


When the pressure gauge is reading 8 - 10 lbs above the clean, starting pressure (after backwashing), it is time to backwash the filter. This process involves turning a valve so that the water will flow through the filter backwards, flushing out the dirt. Hence the name "back-washing." DE filters can have either a push-pull valve (also known as slide valves) or a multiport valve. The multiport valve has multi-ports on the valve, usually 6 positions:

  1. FILTER: Keep it here most of the time, except when backwashing, rinsing or wasting

  2. RINSE: Use this setting for 20 seconds after backwashing to rinse tank

  3. RECIRCULATE: Use this if the filter's broken; at least you're circulating your pool.

  4. BACKWASH: Use this setting to reverse the flow in the filter and send water out of the waste line. Make sure valves are open or hoses rolled out

  5. CLOSED: Put here to close off flow from the pool, usually to work on the equipment. Do not operate pump with valve in closed position

  6. WASTE/ DRAIN: Another filter bypass setting, but this one sends the water out of the waste pipe (hose), instead of returning it to the pool. Used to lower pool water level or to vacuum to waste

So, to backwash a D.E. filter with a multiport valve;
  • Shut off pump motor

  • Press down on valve handle, rotate valve from FILTER to BACKWASH position

  • Roll out any backwash hose or open any waste line valves

  • Open air bleeder assembly on filter, and turn pump on.

  • Watch pressure gauge for backpressure and hose for kinks. Be prepared to shut off pump quickly

  • After hose fills with water, run for 2 - 3 minutes or until water runs clear

  • Shut off pump motor and move multiport valve handle to RINSE position. Run on rinse for 5 - 10 seconds. Shut off pump again, and move handle back to BACKWASH. Turn on pump again until water runs clear. Continue in this fashion 3 - 4 times, alternating between Backwash & Rinse,  to ensure a thorough backwash.

  • Shut off pump motor and move multiport valve handle to FILTER position

  • Turn pump back on and note lower pressure. Roll up backwash hose

  • Add 1 lb D.E. powder per 10 sq ft of filter area. Look on filter tank

To Backwash a DE filter with a slide valve:
  • Shut off pump motor, roll out backwash hose (if you have it)

  • Twist to unlock plunger T-handle, pull/ twist plunger upwards 2 - 3"

  • Open air bleeder assembly on filter, and turn pump on

  • Watch pressure gauge for backpressure (+ 40 PSI) and hose for kinks. Be prepared to shut off pump quickly.

  • After hose fills with water, run for 1 - 2 minutes or until water runs clear. Shut off and push handle back down. Turn pump on and run in filter position for 15 seconds and then shut pump off and  backwash again for 1 min. Filter again for 15 seconds and another 30 second backwash.

  • Shut off pump motor and push T-handle back down into locked position

  • Turn pump back on and note lower pressure. Roll up backwash hose

  • Add 1 lb D.E. powder per 10 sq ft of filter area. Look on filter tank.

A properly sized D.E. filter should, in most cases,  be able to operate continuously for a period of 4 weeks between backwashings. A "Filter Run" of less than 4 weeks may indicate grid problems (or sizing problems). Filter grid fabric can become clogged with Calcium deposits or oils. After removing the grids from the assembly, you can soak in TSP (trisodium-phosphate) and warm water to remove oily deposits. If you have high levels of calcium or other minerals in your pool water you can soak the grids in a 10% muriatic acid solution for a few minutes followed by a full rinse. TSP soak and Rinse will remove mineral deposits such as Calcium.


D.E. powder in the pool?


You either have holes in the fabric of the grids, or a crack in the manifold that the grids attach to. It can also mean a broken air bleeder tube or assembly. Finally, D.E. in the pool can mean that the multiport or push-pull valve is allowing powder to bypass the filter. You will notice this most when adding new D.E. powder after backwashing, but you can test this at any time. The best method to determine the cause is to remove the grids and clean/ inspect thoroughly.


Filter Grid replacement:

Grids and manifolds vary by manufacturer, and by size. DE grids are usually $15-25 per grid; and you may expect to pay $75-100 for a manifold. Labor is usually under one hour. You can buy the entire set of 8 grids for a lower price usually, and many times it is best to replace all grids at one time. When replacing all the grids, do it upside down, with the manifold on the ground, and then work the bottom spreader plate on the top, spacing all grids correctly. If handy with an awl, torn grids can be sewn instead of replaced.


Poor water Quality?


It could be a problem with your multiport or push-pull valve. The valve could be allowing water to bypass the filter and return to the pool unfiltered. Perhaps you are not running the filter long enough. Perhaps there is not enough D.E. powder in the filter, or too much DE powder. You may also need to backwash the filter or remove the grids and clean them manually. Poor sanitation, poor water balance, and pool circulation could be another cause, and it could have nothing to do with the filtering at all.


How long should I run my DE pool filter each day?


Well, just as much as you need. Careful experimentation will show you when the water quality begins to suffer. Many people with smaller, older equipment (filter/ pump) run their systems 24 hours per day. The average (I would guess) would be about 16 hours. BUT! It depends on your system. Undersized? Old? High pool Use? Large Debris Load? Heavy Sunlight? Any of these factors call for extra filtering. If you're too frugal with the electricity, you may have to pay more in chemical costs.

Leaking DE filter?

Most D.E. filters have a belly band clamp with a large O-ring between tank halves. The o-ring can become distended or flattened and may need to be replaced if water is dripping from the center clamp. Caution: Do Not remove the center clamp while the pump is running, and without first releasing pressure inside the tank. You may notice your multiport valve leaking in one or more areas. See sand filter info on previous page. If your push-pull valve is leaking out of the backwash port (where the hose attaches), the plunger either needs replacement, or a new set of o-rings.

If your DE filter tank is leaking, and not from the belly band, bulkhead fittings or air bleed assembly, but in the tank itself, through a pinhole or crack, replace the tank half or entire filter immediately. There is no safe and effective way to repair tank damage.

DE filter powder Swimming Pool DE Powder and Purifiber™ DE Alternative Purifber DE Alternative

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