Multiport Filter Valve Repairs

Sand and D.E. pool filters use a valve that allows the pool owner to reverse flow through the filter to flush out the accumulated dirt. A push-pull valve, also called a Slide valve can be used, but the majority of installed filters will use a Multiport valve, mainly for the reason that it provides more settings than just filter or backwash.

Multiport valves do have a few drawbacks however. Some builders prefer slide valves because they allow for higher flow rates than the many ports of the multiport valve. They are also much simpler to repair and require repair less frequently than multiport valves.


The most common problem with a multi-port valve has to do with the internal gasket, known as a spider gasket. A spider gasket is what prevents water from leaking from one port into the port next to it. The spring loaded diverter presses down on the ridged spider gasket, sealing up each port and directing the water only where it needs to go.

If your spider gasket becomes worn or torn, or twisted or happens to pops out of the groove in the valve body, this allows water to creep and seep from one port to the next.

You may not notice water bypassing the filter, and returning to the pool without being filtered, but this can happen. On D.E. filters, if you notice D.E. powder coming back into the pool when you add it after backwashing, this can be one of the causes, aside from internal filter problems like torn grids, or a missing air bleeder or standpipe o-ring.

The more common problem is that you will notice water coming out of the backwash hose, even after you stop backwashing. Sometimes, just shutting off the pump and slightly repositioning the valve will create a better seal or allow any grit or debris between the diffuser and the gasket to be flushed out. If it continues, it's time to open up the valve and inspect the innards of your multiport valve, specifically the spider gasket.

To inspect your spider gasket, remove the bolts surrounding the lid and by lifting on the handle, pull the entire 'key assembly' from the valve body. You may need some slight prying with a flathead screwdriver to help in removal.

The spider gasket should be firmly attached (glued) into all of the grooves in between the ports. It should not appear twisted or overly worn or torn. Check to see that your gasket is not enlarged or looks as though the rubber has been chemically altered. If so, you should find the source of this, which could be a chlorinator backing up, or it can be caused by pouring chlorine or pH decreaser in through the skimmer, which is a big no-no.

On some Pac-Fab and Jacuzzi multiport valves, the gasket is not below the diffuser, or rotor, but is molded into the rotor itself. This is a superior design, and will likely give the owner fewer problems.

If it looks like you need a new gasket, make notes of any make, model and part numbers listed on the valve. Keep in mind that you may see a part number on the valve label, which may be just that, the part number for the valve label or decal, and not an item number for the valve itself. Nevertheless, this clue can be used as a means to identify the valve that you have.

There are dozens of different spider gaskets made, for dozens of valve models, visit our valve parts department to assist you in finding your correct valve.


  1. Use a small, sharp screwdriver to remove old gasket and bits left behind in the groove.
  2. Dry the groove out with paper towels or a leaf blower or hair dryer.
  3. Dry fit the new gasket to make sure the size is correct.
  4. Place dabs of silicone or superglue in each groove. Not much is needed.
  5. Press new Spider Gasket in place, with flat side down, ridged side up.


In the center of the lid is a hole that the stem of the diffuser sticks up through to connect to the handle. There are two small o-rings that seal up the stem. Occasionally these may leak. If the leak is minor, it may not be worth the time to fix it, but if it bothers you, go through the steps above to identify your valve and order these o-rings, or you can also look for the Go-Kit for your multiport, which contains all of the gaskets, washers and o-rings for a particular multiport valve.


Under the lid of your valve, a spring is used to provide the tension needed to press the rotor into the spider gasket, and also to facilitate the rotation between one setting and another. When you press down on the valve handle to change positions of the valve, you are compressing the spring.

If the valve spring becomes broken, which can happen from chemical corrosion, the handle will be floppy (no tension) and you may experience a problem of water (and debris) making it's way into different ports or coming out of the backwash port. You may also see DE powder coming into the pool, as described above, or bits of debris coming back into the pool while vacuuming or cleaning the skimmer.


The sight lass is the little clear bottle or view glass that allows you to see when the backwash water becomes clear, so you know when to stop backwashing. If your sight glass is leaking during backwashing, it may be missing the small gasket that prevents this, or you may notice a small crack. Is it worth repairing if it only leaks during backwashing? Maybe not, but you can decide this for yourself.


  1. No lubrication is necessary, except on the lid o-ring, after opening the valve for service.
  2. Always shut the pump off before turning the multiport valve.
  3. Drain the valve completely for winterization.
  4. Move the valve handle gently and purposefully.

One more thing, if you are faced with major valve problems, it may be cheaper and faster to replace the entire valve, or what's called the 'Key Assembly', which is everything from the rotor to the handle. Drop it in, tighten it down and you're done.

In The Swim makes every effort to provide accurate recommendations based upon current ANSI/APSP/ICC-5 2011 (R2022) standards, but codes and regulations change, and In The Swim assumes no liability for any omissions or errors in this article or the outcome of any project. You must always exercise reasonable caution, carefully read the label on all products, follow all product directions, follow any current codes and regulations that may apply, and consult with a licensed professional if in doubt about any procedures. In The Swim assumes no legal responsibility for your reliance or interpretation of the data contained herein, and makes no representations or warranties of any kind concerning the quality, safety, or suitability of the information, whether express or implied, including, without limitation, any implied warranties of merchantability or fitness for a particular purpose.