Servicing the Multiport Valve on a Swimming Pool Filter

Problems Are Usually Traced to the Spoke Gasket or O-Ring

Man turning pool cover pump
Wayne pool cover pump. Amazon.com

In most residential swimming pools, the multiport valve is a most important piece of equipment, second only to the pool pump and filter itself. The multiport valve, also known as the Vari-Flo, backwash, or filter control valve, is a multi-purpose fitting that is found on most pools with sand filters or diatomaceous earth (DM) filters. Different settings on the valve allow you to route the water through the filter system in different ways to perform various maintenance operations.

The multiport valve is usually positioned on the top or side of the filter tank, and it features a locking handle that can be turned to any one of several positions, including FILTER, BACKWASH, RINSE, WASTE, CLOSED, and RECIRCULATE.  In some instances, the handle position may be indicated by numbers instead of words. 

Symptoms of Multiport Problems

There are two common problems that occur with some frequency on multiport valves. 

One common symptom of multiport valve problems is when there is leaking around the valve itself, or when water comes out of the waste line, even when the valve is set to the FILTER position. Multiport valve problems may also be indicated when dirt fails to be trapped by the filter, instead returning to the pool.

In most cases, these symptoms occur when the spoke gasket (also called the spider gasket) inside the valve is damaged or worn. This damage is usually caused when a user moves the valve handle to a different position while the pump is running.

When this gasket goes bad, it can cause leaking around the valve, or it can allow dirt to bypass the filter and return to the pool, signaled by perpetually cloudy water. Whatever the precise symptoms, the solution is to replace the spoke gasket. 

Another common problem is when the handle of the multiport gets stuck or is difficult to turn.

The solution here is usually to disassemble the valve and clean and lubricate the parts. 

  • Tip: before attempting either repair, record the details of the multiport valve assembly on paper, or take a photo of the position of the parts as you disassemble it. This will help you reassemble the valve correctly. To make sure the parts are properly aligned during reassembly, you can scribe a line across the parts to register their relative positions. 

How to Replace the Spoke Gasket

  1. First, turn off the swimming pool's filter pump.
  2. Remove the screws or bolts that hold multiport valve lid in place. There are usually six to eight screws or bolts, and you may need a wrench to grip nuts from beneath as you loosen the screws or bolts from above.
  3. After removing the bolts, lift up the handle, bringing the lid and key stem with it. The key stem is the dome-like piece below the lid, and all these parts together are known as the key stem assembly. This assembly is what directs the flow of water to the different ports on the valve.
  4. Look down into the valve and identify the spoke gasket. NOTE: In some valves, the spoke gasket is glued into the key stem. You may find some debris here that prevents the key stem from seating properly on the gasket. By cleaning out this debris, you may solve your problem without going any further. 
  1. Inspect the spoke gasket. It should be intact and completely seated in the grooves in the body of the valve. Check to make sure that the gasket is completely glued in and is not separated from the groove anywhere. If the gasket is worn, torn, or has come unglued and is mangled, you will need to replace it.
  2. As the first step in replacing the gasket, scrape out the old gasket completely. Make sure the grooves are completely dry.
  3. Turn the new gasket upside down (the rounded part is the top side) and apply a light coat of glue completely over the bottom of the gasket. This glue can be most any type that does not break down underwater. PVC glue, often used for plumbing work, is a good choice.
  4. Place the new gasket into the grooves, glue-side down, and seat it properly. Make sure that no glue has oozed out onto the top of the gasket. Do not put any sealant, lubricant, etc. on the spoke gasket, as it will only hold debris on the gasket and prevent it from making a good seal. If the seal isn't good, it will allow water to bypass the filter or leak out the backwash line.
  1. Put the key stem assembly back into the valve, and resecure the bolts or screws.  

Tips for Reassembling the Valve:

  • Are you having trouble remembering 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 should point at the filter tank. If it is a DE filter, the handle should 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 (see below). Do not spread vaseline or another substance on the O-ring, because debris will adhere to it and prevent it from making a good seal. 
  • Wait an appropriate amount of time for the glue to dry before starting up your pump.

How to Fix a Sticky Multiport Valve Handle

If you are having a difficult time rotating the multiport valve handle, there is an easy fix:

  1. First, remove the pin holding the handle to the stem by knocking it out with a hammer or the head of a screwdriver.
  2. With the handle off, undo the screws or bolts holding the stem assembly; this will allow you to lift off the cover. The entire key stem will probably come along with the cover because the shaft of the key stem is likely gunked up.
  3. Separate the key stem from the cover; you should see a small O-ring on the shaft. NOTE: If the valve has been leaking through the stem, this is the culprit. You will see a spring that holds the key stem down on the spoke gasket when assembled.
  1.  Remove the old O-ring if needed and thoroughly clean the shaft, O-ring, spring and the hole of the cover. Lubricate the new O-ring with Jack's Lube, Aqualube, or a similar product. (While Vaseline will work, it dissolves in water fairly rapidly.)
  2. Place the key stem back in the valve. For a sand filter, the holes in the key stem should face toward the filter tank; for a DE filter, the holes should face away from the tank.  
  3. Put the spring and washers (if present) back on the key stem.
  4. Put the cover back on (check the position of the cover O-ring), so that the filter position is over the opening in the key stem. Evenly tighten down the screws or bolts.
  5. Put the handle back on in the filter position, and replace the pin that holds the handle in place.