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Why Is My Multiport Valve Leaking?

Leaking Pool Filter Valve

Multiport valves are the main water route interchange for your pool water. If the water needs to be forwarded, reversed or drained out, it will need to be done through this valve. The routing system inside a multiport valve is essentially water’s equivalent to chutes and ladders.

These valves have as many as seven “positions” but for the most part the average pool owner will only use a handful of these.  Here is a list and explanation of the most often used positions so we have a solid footing moving forward: 

  • Filter – The standard operation mode; the water is cycled from the pump through the filter media and back to the pool.
  • Backwash – This selection is the cleaning cycle. The flow of the water is brought in from the pump  then routed to enter the filter reverse to the normal direction. This effectively begins to loosen and eventually eject dirt through the waste port.
  • Rinse – Rinse returns the normal flow of water through the filter but it maintains the exit flow routed to the waste port.  After a backwash some particles may still be left in the pipes so to avoid that dirt being ushered to the pool, we need to rinse.Picture1

The Spider Gasket

If the valve is the highway interchange of your water then the spider gasket would be the guard rail. These gasket spokes act as dividers to ensure the path of the water stays true.  If your multiport valve has a drip coming from the waste port line, most pool technicians will jump for the spider gasket.

The spider gasket is located either on the diverter pinwheel or the base of the valve the diverter faces.  When we select a function on a multiport valve and release the handle, we drop the diverter onto the spider gasket.  If the gasket has become worn and warped then the water will seep through the seam and end up in the waste.

The Fix: The solution is pretty simple, replace the gasket. Some gasket replacements are simple, remove the valve cover and old gasket, then lube in a new one. Other gaskets are glued into the diverter which requires a few extra steps.  If you want a step by step guide on the different ways to replace a spider gasket read this: How to Replace a Spider Gasket on a Multiport Valve

The Diverter Spring

That tension we feel when spinning the selector handle is created by the diverter spring.  Besides making it hard to spin the handle, the spring serves the purpose of locking

Picture2the diverter against the spider gasket. If the spring in your valve is worn, it may be causing a seam between the diverter and gasket which shows itself in the form of a leak out the waste port.

The Fix: Replace spring, which to be honest, is not fun at all.  The spring is sandwiched on the diverter assembly which means it must be disassembled and assembled again. The hard part is getting the spring depressed enough to secure the handle pivot rod.  If you are feeling brave and want to attempt a spring replacement, please follow our guide: How To Replace a Pool Multiport Valve Spring

Valve Cover

The valve cover o-ring is found in the seam between the valve cover and main housing.  If water is found leaking from this seam then this gasket would be your culprit.  To access the gasket we would simply remove the 6 – 8 screws on the valve cover to remove it, peel out the o-ring, clean the groove, lube the new o-ring and re-attach screws.

The Fix: Read an inch above this line.

Valve to Filter Connection

Whether the valve is a top mount or a sidemount, it has to connect to the filter somehow.  At that joint connection there is a gasket holding on for dear life.  Because of the high flow at these connections, a blowout is somewhat common and easy to spot.

The Fix: Remove the valve from the filter and replace gaskets. Hopefully, the valve is piped in with unions so its removal is not a pain in the neck.  Once the valve is off, find the gasket and apply a freshly lubed replacement.

Thanks for skimming through our pool musings. If you have any further questions about pools, valves or otherwise, feel free to give us a call at 877-372-6038.

author avatar
Matthew Simmons Technical Writer & Pool Product Expert
Swimming pool expert at InyoPools and host of Poolside Chat, brings over a decade of experience in the pool industry.

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119 responses to “Why Is My Multiport Valve Leaking?”

  1. Victoria Avatar

    why does it leak from the top by the handle? I have a pentair sm10-2de
    thanks

    1. Matthew Simmons Avatar

      The most likely causes would be the displaced/broken spring, damaged handle washer, damaged handle-to-stem gasket, or cracked valve cover.

  2. Valerie Avatar

    A mouse got in through my waste pvc pipe and chewed a tiny piece of the spider gasket. The local pool company says they don’t replace just the gasket due to issues with the glue and want to replace the entire multi port. I was planning to add a valve to the pvc waste line to keep the mouse out in the future. Could this valve also solve the leak issue since while the valve is closed the water can’t escape? I don’t have any leakage in recirculating mode, just in filtration mode (which is adjacent to the chewed bit).

    1. Valerie Avatar

      For anyone reading this in the future, I tried this approach and the water was diverted into the site glass which blew off. At least the shutoff valve will prevent the mouse from getting back in there.

  3. Mike Avatar

    I a Pentair Quad DE 60 filter and have lived in this house for 7 years now . This year I’m having trouble w the water being cloudy despite perfect chemistry, cleaned cartridges and new DE, frequent backwashes and DE replacement. I’m wondering if I have a DE leak somewhere in the system. And I happened to notice that my multi port valve is a SM10-3 SAND (USE ON SAND FILTER ONLY!) I guess the previous owner forgot to change it to a DE compatible multi port valve when they changed to DE filter? … but it seems like it’s been working fine for past 6-7 years. I guess my question is, can this mismatch cause a DE leak, and perhaps a delayed one like I’m getting now? Should I replace it w the correct multi port regarhdless? I’m going to go ahead and replace my DE cartridges since they are 7+ years old and could be a cause of water cloudiness if they’re not running efficiently or have a hidden leak causing DE to escape. Thanks for any help/advice

    1. Matthew Simmons Avatar

      The mismatched valve wouldn’t be a factor in your case just because though it may say “sand only,” it can be used on DE filters as long as the In and Out port measurements and orientation match up, the valve should work as required. And as you mentioned, it had been working for years, so this blip should have happened a long time ago if it was an issue.

      While the pump is running, I would put my hand down by the return to see if there is a noticeable spray of DE in the returning water. Is there water flowing from your backwash pipe when the valve is set to normal filtering? If it is leaking water, then that could be a sign of a corrupted spider gasket or diverter spring. Check the handle; if it is jiggly, the diverter spring is not operating as it should.

      A bad combination of pool chemicals can also cause milky/hazy water. I know you said the chemistry is perfect, but it never hurts to double-check. Bad combos: High pH + High Calcium, High pH+ Low Chlorine, Low Chlorine + Low Stabilizer (CYA)

  4. Samantha Avatar

    When I backwash, then rinse then turn back to filter the water continues to trickle out the waste port. Sometimes if I pull up on the handle hard it won’t leak. I don’t know if that has anything to do with it not leaking or is a coincidence. What do you think it could be?
    Thanks

    1. Matthew Simmons Avatar

      Yes, that is probably a sign you have a loose handle/diverter spring which is something we cover in the article.

  5. Jim Booth Avatar

    I had water leaking form the waste line. I replaced all the gaskets and the spring. There is still water leaking from the waste line. I do not detect any broken grooves in the spider gasket. Thoughts?

  6. Matt T Avatar

    I have a leak through the waste port as well as at the coller where the multiport connects to the filter housing. I had neither issue last year when closing. It’s odd that the the spider gasket and the oring gasket at the bottom both whent the same year, right? I don’t want to purchase the gaskets if I need to replace the entire multiport… Thoughts?

  7. LaVonne Criss Avatar

    My pool services guy told me I have too replace the whole Hayward top. When filtration is on it leaks like a stream down the grey system. Is this true or do I just need a new valve.

    1. Matthew Simmons Avatar

      I am going to presume the “grey system” is referring to the waste line. So that could be a few things that I mention in the article, the spring, diverter steam, spider gasket. You should take a look at it yourself or have them explain exactly what was wrong with it.

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