Mulitport spider gasket/sand in pool??

[deadrabbit]

I have a 7 year old Sta-Rite 240BP sand filter with a 112-148 multiport valve. Last year I noticed a small amount of sand in the bottom of the pool but it was very slight and manageable. Opening the pool this year, I decided to replace the sand and inspect the laterals. The laterals looked great. I thoroughly cleaned all of the parts and replaced the sand with pavestone pool filter sand from Home Depot. I started the pump on backwash and allowed it to run for several minutes, rinsed, backwashed a second time, rinsed again, and finally set the vale to filter. After 24hrs of run time, I noticed sand build up on the stairs and edges of the pool liner. I removed the sand by vacuuming to waste. It’s been another 48hrs and more sand has accumulated. I found that the spider gasket is damaged and needs to be replaced. There is no water leaking but the gasket looks horrible (probably 7 years old). I found a few sites saying that the gasket could cause sand to enter the pool. I asked around at my local pool places and they said there is no way the bad gasket could cause sand to enter the pool. I haven’t replaced the gasket but will in the next few days. Could this be my problem??

Also, Home Depot lists pavestone sand on their website as 50lb bags. I weighed the bags to make sure and found them to be only 40lbs!!

Thanks for the help

 

[JasonLion]

Sand shouldn't be coming out of the filter at all in any mode, so it shouldn't matter what the spider gasket does, or fails to do. DE is different. DE can get into the pool when you have a bad spider gasket, especially when you are backwashing.

One good double check is to tie a stocking to one of the returns. If sand is coming out of the filter, it should get caught in the stocking where you can see it. If, on the other hand, sand is somehow blowing into the pool from somewhere else, there won't be any sand in the stocking.

 

[JohnT]

I have a 7 year old Sta-Rite 240BP sand filter with a 112-148 multiport valve.

Welcome to TFP


I have the same filter and valve. I believe you'll find the multiport gasket is replaced as part of the plug assembly on that valve. You can see a parts breakdown HERE

I've had some issues with dirty bypassing my filter while vacuuming this year, so I've been inside and spent quite a bit of time thinking about it, and I agree with Jason that the multiport can't let sand through, unless maybe the pump is too large or there is too much sand in the filter.

Barring those two options, I believe you either have a damaged lateral or a crack in the collector hub assembly.

 

[deadrabbit]

Thanks for the input. This forum seems to be a good place for valuable advice. I bought a new plug/gasket today and I am impressed with the quality compared to the glue-on type. I think I will try the stocking trick tomorrow. If sand is passing, I guess the best thing to do will be to just go through the filter one more time. One place that I may have overlooked is the bottom of the collector hub assembly. Is this a common site of cracking? Maybe I focused too much on inspecting the fragile laterals…

The sand I bought was cheap Home Depot sand ($6.00 per bag). Could there be a difference in the processing quality/deviation of particle size in different brand sands? If so, could cheap brands contain many more small particles of sand that will pass through the filter (and eventually be eliminated through vacuuming)?

If the spider gasket is leaking and I am backwashing, could some backwash enter the pool supply line? Would this blow some sand into the pool after rinsing and changing back to filtration?

 

[JasonLion]

A sand filter is designed so that there is enough "headroom" above the sand so that no sand will ever come out of the filter when backwashing (assuming everything is setup correctly). When backwashing, lots of dirt and debris will come out of the filter, and a bad spider gasket would tend to let a little of that into the pool. But there shouldn't be any sand in with the dirt/debris.

As JohnT mentioned there are two ways the filter could be setup wrong, without being broken, and let sand out. One is if the pump is too large, but that would have been a problem before. The other is if you added too much sand when you refilled the filter. Sand filters are normally setup to have the sand come up to a specific height inside the filter. Often the amount of sand you add needs to be adjusted slightly so that it comes up to the right height, regardless of what the spec says about "add X pounds". Check your filter manual and see what height the sand is supposed to come up to and check to see if you filled it too full.

Another place to look for problems in a sand filter is the central pipe. In many sand filters the central pipe has a slip joint. If your filter is like that, check to make sure that slip joint is fitting tightly together. Sometimes they get just loose enough to let a little sand through there. The same kind of thing can happen in some designs at the point where the laterals meet the main pipe. Make sure those joints are tight and won't let sand through.

 

[deadrabbit]

Ok, replaced the gasket, vacuumed, filtering and waiting to see what happens. I thought about the pump size and did a quick calculation. I live in Alabama so the guys who installed the system may have just guessed, no pun intended. I haven’t measured the vacuum yet but according to my out-put pressure/filter specs I would have to have a vacuum reading of 23.803 inches of mercury to get within the limits of the filter. Seems kind of high. Also, that is based on a generic performance chart for a 1HP pump on the poolplaza site.

Max filter flow rate is 62gpm. 1HP pump 25feet from pool and 10psi output. The pump is a Flotec and I haven’t been able to find a performance chart.

I’m going to measure the vacuum in a few days and I don’t think it will be high enough. From what you guys are telling me, this could be my problem.

 

[i2macpherson]

A sand filter is designed so that there is enough "headroom" above the sand so that no sand will ever come out of the filter when backwashing (assuming everything is setup correctly). When backwashing, lots of dirt and debris will come out of the filter, and a bad spider gasket would tend to let a little of that into the pool. But there shouldn't be any sand in with the dirt/debris.

As JohnT mentioned there are two ways the filter could be setup wrong, without being broken, and let sand out. One is if the pump is too large, but that would have been a problem before. The other is if you added too much sand when you refilled the filter. Sand filters are normally setup to have the sand come up to a specific height inside the filter. Often the amount of sand you add needs to be adjusted slightly so that it comes up to the right height, regardless of what the spec says about "add X pounds". Check your filter manual and see what height the sand is supposed to come up to and check to see if you filled it too full.

Another place to look for problems in a sand filter is the central pipe. In many sand filters the central pipe has a slip joint. If your filter is like that, check to make sure that slip joint is fitting tightly together. Sometimes they get just loose enough to let a little sand through there. The same kind of thing can happen in some designs at the point where the laterals meet the main pipe. Make sure those joints are tight and won't let sand through.

I am trying to fond out on the web what the slip joint on central pipe looks like. Cam't finf any image. I am experiencing that fine particle problem in the pool and i worried about something that might be a kind of O-ring that the dog brought back...... last year !