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How to Service A Swimming Pool Filter's Multiport Valve

How To Treat A Problem With Your Swim Pool Multiport Valve

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Next to your swim pool pump and filter, the multiport valve is a swimming pool systems most important piece of equipment. The multiport valve is also known as a Vari-Flo valve, backwash valve, or filter control valve. It is important that it operates easily and properly. Some of the common problems caused by a malfunctioning multiport valve include water leaking out of the backwash line, dirt returning to the pool when vacuuming, and water that never clears up. This article will help you service and repair these problems associated with your swimming pool multiport valve.

Most problems associated with the multiport valve have to do with water leaking by the spoke - sometimes called spider - gasket inside the multiport valve. This can allow dirt that you have just vacuumed up to bypass the filter and return to the pool. It also can make the water very difficult to clear up because some dirt is always bypassing the filter. Now, we will tell you how to open up and service this valve, but before you start, heed this advice from a pool owner:

Record the details or take a photo to help prevent re-assembling the valve incorrectly; you could also scribe the top and bottom assemblies with a line.

  • First, turn off the pump.
  • There are usually six to eight screws or bolts that hold the lid of the valve on. To remove these you may need to hold a wrench to the nuts that are underneath the lid and screwed onto the bolts.
  • After removing the bolts, you will be able to lift the handle bringing the lid and key stem with it. The key stem is the dome-like piece below the lid and all of this is called the key stem assembly. This is what directs the flow of water through the valve.
  • Look down into the valve and you will see the spoke gasket. NOTE: In some valves the spoke gasket is glued into the key stem. There may be some debris here that is not allowing the key stem to seat properly on the gasket. By cleaning out this debris, you may solve your problem.
  • Inspect the spoke gasket. It should be whole and completely seated in the grooves in the body of the valve. Check to make sure that the gasket is completely glued in and does not come out anywhere.
  • If the gasket is worn, torn, or has come unglued and is mangled, you will need to replace it.
    1. To replace it, first scrape out the old one completely.
    2. Now make sure the grooves are completely dry.
    3. Turn the new gasket upside down (the rounded part is the up side) and apply a light coat of glue over the complete bottom. This glue can be most any glue that does not break down underwater (we typically used PVC glue because we carry it for plumbing work).
    4. Now, place the gasket into the grooves, glue side down and seat properly. Make sure that no glue has oozed out and gotten on top of the gasket.
    5. Do not put any sealant, lubricant, etc. on the spoke gasket. It will only hold debris to the gasket and will not make a positive seal, allowing water to bypass the filter or leak out the backwash line.
    6. Then, put the key stem assembly back in and tighten down the bolts evenly.
  • Don't remember which way to point the handle when putting the key stem assembly back in? For a sand filter, the handle when in the FILTER position will point at the filter tank. If it is a DE filter, the handle will point away from the filter.
  • When putting the key stem assembly back in, make sure that the O-ring under the lid is clean and in the proper position. If this O-ring looks cracked or crimped, this would be a good time to replace it. Do not goop this O-ring up with a bunch of Vaseline, etc. This can make it easier for debris to stick to it and it will not make a good seal.
  • You will need to wait an appropriate amount of time for the glue to dry before starting up your pump.
If you are having a difficult time rotating the multiport valve, there is an easy fix.
  • First, remove the pin holding the handle to the stem by knocking it out.
  • With the handle off, undo the screws or bolts which will allow you to lift off the cover.
  • The key stem will probably come with it because the shaft of the key stem is gunked up.
  • Remove the key stem from the cover, and you should see a small O-ring on the shaft.NOTE: If the valve has been leaking through the stem, here is the culprit.
  • You will also see a spring that holds the key stem down on the spoke gasket when assembled. Replace the O-ring if needed and thoroughly clean the shaft, O-ring, spring and the hole of the cover.
  • You will want to lubricate the O-ring with Jack's Lube, Aqualube, or a similar product.
  • While Vasaline will work, it dissolves in water fairly rapidly.
  • Place the key stem back in the valve with the hole in it towards the filter tank for a sand filter and the hole away from the tank if it is a DE filter.
  • Put the spring and washers (if there were some) back on the key stem.
  • Put the cover back on (check the cover O-ring) with the filter position over the opening in the key stem and evenly tighten down the screws/bolts.
  • The handle will now go on in the filter position, and you can replace the pin that holds it on.

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