Sand filter leaking out of backwash port.

[Isabella]

Hey folks, my sand filter just started dripping water out of the backwash port even though the valve is set to “Filter.” It’s not a lot, just a steady trickle, but I’m worried it’ll get worse. Do I need to replace the whole multiport valve, or is there a smaller fix for this?

 

[Freddie]

Hey folks, my sand filter just started dripping water out of the backwash port even though the valve is set to “Filter.” It’s not a lot, just a steady trickle, but I’m worried it’ll get worse. Do I need to replace the whole multiport valve, or is there a smaller fix for this?

That’s usually a bad spider gasket inside the multiport valve. Over time they warp or tear, and water sneaks past into the backwash line. You don’t need to replace the whole valve unless the body is cracked just open it up and swap the gasket. Cheap part, not too hard to do.

 

[Zephyr]

Hey folks, my sand filter just started dripping water out of the backwash port even though the valve is set to “Filter.” It’s not a lot, just a steady trickle, but I’m worried it’ll get worse. Do I need to replace the whole multiport valve, or is there a smaller fix for this?

I had the same drip last summer, replaced the spider gasket, and it was fine. Just make sure you lube the new gasket lightly with silicone pool lube so it seats better. While you’re in there, check the spring in the handle too, since a weak spring can also cause leaks.

 

[Isabella]

Thanks both! That makes me feel a lot better.

I had the same drip last summer, replaced the spider gasket, and it was fine. Just make sure you lube the new gasket lightly with silicone pool lube so it seats better. While you’re in there, check the spring in the handle too, since a weak spring can also cause leaks.

That’s usually a bad spider gasket inside the multiport valve. Over time they warp or tear, and water sneaks past into the backwash line. You don’t need to replace the whole valve unless the body is cracked just open it up and swap the gasket. Cheap part, not too hard to do.

Thanks both! That makes me feel a lot better .

 

[Lily Allen]

I’ve had that happen too, it was the spider gasket. Replaced it and the leak stopped immediately. Make sure you check the spring in the handle too sometimes the weak spring can cause leaks as well. Anyone else lube the new gasket with silicone pool lube?

 

[Brandon Hayes]

Yep, everyone’s pointing you in the right direction already A slow trickle out of the backwash line while in Filter is almost always the spider gasket starting to fail.

One extra thing I’ll add from experience: if the valve handle has ever been turned while the pump was running (even once), that can damage the gasket pretty quickly. It doesn’t cause an instant leak every time, but weeks or months later you’ll suddenly notice exactly what you’re seeing now.

When you open the valve:

• Take note of how the old gasket sits before pulling it out (a quick photo helps).
• Clean the channels really well before installing the new one.
• Light silicone pool lube only, no petroleum grease.
• Let the glue or gasket settle fully before restarting the pump if the gasket is the glued-in type.

Also, after replacing it, always turn the pump off before changing valve positions going forward. That alone can make the new gasket last years instead of one season.

You definitely don’t need a whole new multiport unless the valve housing itself is cracked, which is pretty rare. This is one of those annoying but thankfully cheap and fixable pool issues.

 

[Ivy Adewale]

Usually you do not have to replace the whole valve. A steady drip out of the backwash port is often just the spider gasket inside the multiport wearing out or getting twisted, so water “leaks” into the backwash line even when it is set to Filter. If the valve body is not cracked, you can usually open it up and replace just that gasket (it is a cheap part). When you install it, I usually use a light coat of silicone lube so it seats clean, and I also check the handle spring while I am in there, because a weak spring can contribute to leaks too.