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  Swimming Pool Repair Tips


Diatomaceous Earth Swimming Pool Filters

(DE) filters: The DE 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. As with sand filters, the pressure gauge indicates a need for backwashing when it reads 8-10 lbs. higher than its clean reading. After backwashing a DE filter, a new application of DE filter powder is added to the filter by pouring into the skimmer. An annual breakdown of the filter is necessary to thoroughly clean DE filter grids with a garden hose.

A DE filter requires that the operator (you) add DE 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. 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 DE and enters the grid it leaves the dirt, trapped in the DE powder "cake" or coating.

The DE powder is what filters your pool water in a DE filter. Do not operate your pump without having the DE 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 DE 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 DE that is clogged up with the dirt. After backwashing thoroughly, add new DE powder to the filter through the skimmer. If using biguanides (Soft Swim or Baquacil, you will need twice annually, a very thorough cleaning to prevent the filter grids from "gumming up". All DE 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 from the hardware store, but do not use TSP if you are using a biguanide sanitizer). Rinse thoroughly before reinstalling grids into tank.

When backwashing a DE filter, do the "process" several times. That is, backwash until water runs clear, move the multiport valve or push-pull valve to FILTER and run it on filter for a 10-15 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/DE out of the filter, giving you a better, more thorough backwash. If you backwash into a separation tank, this will reduce the flow and thus the efficiency of the backwashing. In this case, break down the filter and hose off the grids twice annually.

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. Sand filters can have either a push-pull valve (aka slide valve) or a multiport valve. The multiport valve has multi- ports on the valve, usually 6 positions:

FILTER: Keep it here 99%, except when backwashing, rinsing or wasting.
RINSE:   Use this setting for 20 seconds after backwashing to rinse tank.
RECIRCULATE: Use this if the filter's broken; at least you're circulating.
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 backwash hoses rolled out.
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.
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 the pool to waste.

So, to backwash a DE filter with a multiport valve;

  1. Shut off filter pump motor.
  2. Press down on valve handle, rotate valve from FILTER to BACKWASH position.
  3. Roll out any backwash hose or open any waste line valves.
  4. Open air bleeder assembly on filter, and turn filter pump on.
  5. Watch pressure gauge for backpressure and hose for kinks. Be prepared to shut off the filter pump quickly if something is amuk.
  6. After hose fills with water, run for 2-3 minutes or until water runs clear
  7. 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.
  8. Shut off pump motor and move multiport valve handle to FILTER position
  9. Turn pump back on and note lower pressure.
  10. Add 1 lb DE powder per 10 sq ft of filter area. Roll up backwash hose.

To Backwash a DE filter with a slide valve;

  1. Shut off pump motor, roll out backwash hose (if you have it).
  2. Twist to unlock plunger T-handle, pull / twist plunger upwards 2-3".
  3. Open air bleeder assembly on filter, and turn pump on.
  4. Watch pressure gauge for backpressure (+40 psi) and hose for kinks. Be prepared to shut off pump quickly.
  5. 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 secs and then shut pump off and again backwash for 1 min. Filter again for 15 secs and another 30 second backwashing.
  6. Shut off pump motor and push T-handle back down into locked position.
  7. Turn pump back on and note lower pressure.
  8. Add 1 lb DE powder per 10 sq ft of filter area. Roll up backwash hose.

To Backwash a Hayward Perflex DE filter

  1. Shut off filter pump motor, roll out backwash hose (if you have it).
  2. Open drain valve on bottom of filter, or remove drain plug.
  3. Pump bump handle on top of Perflex filter several times.
  4. Turn on pump for 5-10 seconds.
  5. Pump bump handle again.
  6. Repeat several times until clear. Close drain valve or replace plug.
  7. Add DE filter powder in proper amounts with pump running.

A properly sized DE 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 filter grid problems (or sizing problems). Filter grid fabric can become clogged with Calcium deposits or oils. Removing the grids from the assembly, you can soak in TSP (do not use TSP if biguanide sanitizers are used) and warm water to remove oily deposits, or you can soak in a 10% muriatic acid solution for a few minutes followed by a full rinse and TSP soak and rinse to remove mineral deposits such as Calcium.

DE 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, DE 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 DE 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 can be expensive. $25-45 per grid; up to $100 for a manifold. Labor is usually under one hour. If handy with an awl, torn grids can be sewn instead of replaced.

Filter is clogging up rapidly; high pressure very soon:  You may have clogged pores in the fabric. First hose grids or hayward Perflex "fingers" very thoroughly clean. Then soak grids in a degreasing solution such a TSP or Simple Nine or commercially available filter grid cleaner. Hose thoroughly and then soak in a 10% solution of Muriatic acid. Repeat if necessary. Hose clean thoroughly again. Use high pressure hose or a pressure washer (below 2000 psi) Reassemble pool filter and add DE filter powder in proper amounts.

Poor water Quality? It could be a problem with your multiport or push-pull valve. It 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 DE powder in the pool filter, or too much. Perhaps you need to backwash the filter or remove the grids and clean them manually. it could also be poor sanitation and poor water balance and pool circulation, and have nothing to do with the filtering at all. Remember: filtration+sanitation+circulation = :-)

How long should I run my 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? No pool cleaner? Poor circulation? Low level of active sanitizer (chlorine) being used? 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. Remember: filtration+sanitation+circulation = :-) They all work together.

Leaking filter? Most DE 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 above. 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.

Plunger replacement: Varies by manufacturer. Around $120.

Filter replacement: DE filters are more expensive than sand filters. You may want to replace if your filter is old and tired, or you may decide to upgrade efficiency from a sand or cartridge filter. Price varies by manufacturer; however, as an example, we sell the  Pac Fab FNS 48 for $449.

copyrighted information provided courtesy of poolcenter.com


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