Spider Gasket Replacement


New member
May 29, 2015
I recently had to change the sand in my Waterco S600. When I turned on the pool filter after putting everything back together, the filter was working well but water was also running out of my waste/backwash line. Assuming it was the spider gasket, I put in a new one but there still was a fair bit of water running out of waste/backwash line. The spring on the multiport valve looks intact and there appears to be no wearing in the divider walls. I recently double checked the spider gasket and noticed that it was not well glued into place (I used glue sparingly). Hypothetically, does anyone out there think that potentially this could be the problem (i.e., water lifting the spider gasket up from its seat under pressure)? My pool company can't do a service call for over a week due to heavy workload so being able to figure it out would be great. Thanks!

Bama Rambler

Mod Squad
TFP Expert
Bronze Supporter
LifeTime Supporter
Jun 22, 2009
SouthWest Alabama
If you didn't change the spring it could be weak and allowing the diverter to lift under pump pressure. I'd go ahead and change it just to be sure.


Platinum Supporter
TFP Guide
Jul 30, 2014
Monmouth County, New Jersey
Please keep us posted after you change the spring. This happened to a friend of mine, upon opening the pool water was gushing out. In turn, I created a Union and dummy pipe (closed off my backwash hose). When I backwash (twice a year), I grab my 27 gallon bin with everything in there and in about 3 minutes I am up and running. This ensures that if the gasket was to go bad or the spring (I just learned something), water will stop at the backwash hose.

One day I did not have the MPV on filter and turned on the pump. After shutting off quickly, I was getting water out of the backwash hose, but it appears nothing is coming out of the sight glass or hose at this point as I checked. The good news is that at least my pool will not be down if this happens (I think) that the water will still run through the filter if it can be stopped at the backwash hose. Only time will tell. The part to the left is glued into a small 2" pipe that is threaded to the MPV. Works like a charm. Comes out, down on a 90*, back on a 90* and out. With 3 unions, I can swivel the house to backwash anywhere. I also took a 20' very sturdy hose (used from my friend), and a few adapters with a 40' vacuum hose and I am out over 80'. Also, rolling up the hose is so easy when water comes right out of it.

Please keep us posted and good luck!


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In The Industry
Jul 20, 2017
Windsor, Ontario. Canada
I guess there are different set ups but for most once the pressure builds up it will push down on the spider gasket and help a weak spring do its job. What i have seen is once a spring is weak the water will leak around the channels in the head ( the only one we can see is the backwash outlet ) BUT it can be bypassing into others as well, and as the pressure comes up the backwash leaking "usually" stops. That is a spring on the start of getting weak. Once it gets worst the water can continue to get out of the proper channel and you'll see it in the backwash. Unless you have a crack or a chip taken out of the chambers in the head then it has to be the spider gasket or the spring. You might be able to push down on top of the handle to help the spring in the seating of the gasket just to prove a point.