Seal between sand filter standpipe and multiport valve?

[inderpoelchesapeake]

I have a Hayward Pro series sand filter. Is there supposed to be an O-ring or other seal between the standpipe and the multiport valve? If not, what prevents pump pressure from forcing water and fine sediment directly through the standpipe/multiport valve junction rather than being forced down through the sand and into the laterals? I see extremely fine brown "dust" being blown out of the return jets when the pump starts after being off at night and the bottom of the pool accumulates a fine coating of "dust" that is easily blown away by water movement.

• I regularly check combined chlorine and it's always zero. I have also done an OCLT and there was no drop.
• I have replaced the spider gasket/key and the filter sand recently.
• I have several crape myrtle trees, nandinas and other plants in the beds around the pool and I suspect that the fine dust that I fight every summer comes from them. It seems to me that either the filter media is unable to filter out sediment that fine or the sediment is bypassing the sand.
• Pool has been open for 10 weeks and the sand filter gauge pressure has only increased about 1 psi. Is this normal?
• Pool is SWG, vinyl liner, FC 5.5, pH 7.6, TA 60, CYA 70, CH 200.

 

[Texas Splash]

Is there supposed to be an O-ring or other seal between the standpipe and the multiport valve?

No, only the O-ring at the top for the collar. The center pipe should fit fairly snug into the base of the MPV and also sits inside enough to where debris shouldn't get in there. Plus the sand shouldn't be so high that it's close to that area either. In filter mode, water pours over the sand and is pulled upwards through the laterals. The sand captures the fine sediment while the laterals keep the sand in-place. Of course at backwash it's all the opposite.

You probably confirmed it's just a fine sediment and not actually sand correct? Do you see any of this dust/sediment material around the pool as well? The new sand was backwashed and rinsed really well right? After all of that, have you ever tried adding a little DE to the sand to see if that helps?

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[inderpoelchesapeake]

No, only the O-ring at the top for the collar. The center pipe should fit fairly snug into the base of the MPV and also sits inside enough to where debris shouldn't get in there. Plus the sand shouldn't be so high that it's close to that area either. In filter mode, water pours over the sand and is pulled upwards through the laterals. The sand captures the fine sediment while the laterals keep the sand in-place. Of course at backwash it's all the opposite.

You probably confirmed it's just a fine sediment and not actually sand correct? Do you see any of this dust/sediment material around the pool as well? The new sand was backwashed and rinsed really well right? After all of that, have you ever tried adding a little DE to the sand to see if that helps?

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My understanding is that water is not pulled into the laterals by suction, rather it is pushed down through the sand and into the laterals by pump pressure from the top of the sand layer. Thus, it seems possible that water could be forced in between the junction of the standpipe to MPV. Adding DE would increase water pressure above the sand and make it more likely that fine debris might be forced up into the MOV if there was indeed not a tight seal.

 

[Texas Splash]

Yes, water pushed not pulled up & through the standpipe. Bad descriptor on my part. But unless your center pipe (or MPV) have a groove at the top for an O-ring, they just slip into one another. Usually we see more problems with those two being stuck and difficult to separate. If you are concerned about the potential of anything getting pushed up and into that mating area where the pipe and MPV meet, I suppose you can try a wrap or two of Teflon tape around the top of the center pipe or perhaps a thin layer of silicone before assembly.

 

[1poolman1]

Unless your pump is running 24/7 and at a speed that always has the skimmer "skimming" (and the weir is in place) and is the perfect pool, there will always be some debris that will end on the bottom of your pool. Debris falls into the pool 24/7. If the skimmer doesn't catch it it starts to fall to the bottom. Some is not visible to the eye until it has been in the water for a bit and reacted with the chemicals. Even with a rinse after a backwash, some small amounts of debris may return to the pool with a sand filter, especially the dust that comes off of plants. You just get used to it.

The only pools that I ever serviced that were "always" clean were indoors or had large enclosures built over them (like many in Florida). Even then, when they got used, if people didn't wash their feet the bottom got dirty. The more beautifully landscaped the pool area, the dirtier the pool, unfortunately.

 

[inderpoelchesapeake]

Unless your pump is running 24/7 and at a speed that always has the skimmer "skimming" (and the weir is in place) and is the perfect pool, there will always be some debris that will end on the bottom of your pool. Debris falls into the pool 24/7. If the skimmer doesn't catch it it starts to fall to the bottom. Some is not visible to the eye until it has been in the water for a bit and reacted with the chemicals. Even with a rinse after a backwash, some small amounts of debris may return to the pool with a sand filter, especially the dust that comes off of plants. You just get used to it.

The only pools that I ever serviced that were "always" clean were indoors or had large enclosures built over them (like many in Florida). Even then, when they got used, if people didn't wash their feet the bottom got dirty. The more beautifully landscaped the pool area, the dirtier the pool, unfortunately.

Thanks. I suspect that the plant dust is just so fine that it passes through the filter.