Filter putting sand in pool - no luck so far with troubleshooting

Papacheeks

Active member
Jun 28, 2022
28
Michigan
Pool Size
8000
Surface
Vinyl
Chlorine
Liquid Chlorine
I'm trying to figure out what is causing sand to return to my pool. A few weeks back I began communication with my filter/pump manufacturer, but their support is terribly slow to respond. While I'm waiting on their response (sent a message 2 days ago fyi) I'm taking steps on my own to get to the bottom of my problem. I've read tons of threads, and watched videos on installation.

Last year I purchased a brand new pump & sand filter - but unfortunately had problems all season with small amounts of sand ending up back in the pool no matter how often we vacuumed to try and get rid of it. It was mid season, so starting a replacement then would've guaranteed a green pool that would've been more costly to fix than a small bit of sand (or so I believe). At the end of the swim season, this fell off my plate and I intended to circle back to the issue this season, which is where I'm at now.


This year - I took the filter completely apart and inspected all the parts (MPV, Standpipe, Laterals) to see if I noticed any cracks or defects and unfortunately I did not. I reinstalled, per manual specs, and turned my device back on. Initially, I thought the problem was fixed, but then after day 2 or 3 I unfortunately started getting sand back in the pool! Also - last year and this year - I did do a backwash/rinse before filtering to ensure any particulate was settled and not shot back into the pool.



My question is - if all parts are intact, proper sand grit (silica #20) and filled to the proper locations - is there any other cause that could put sand into my pool?
*** The only thing with my filter that has me uneasy, is the fitment of the standpipe to the MPV - I feel this is looser than it should be. Loose in the fact that, if I were to put the standpipe into the MPV I do not think it would hold itself in from the weight alone - it would fall out. I feel this connection should be more secure.***


I've done multiple vacuums to waste to ensure that the sand in the pool isn't just recirculating the same sand through it.




Here's Info about pool:

Aboveground 10k gal (21' Round)
3000gph Pump + Sand Filter
HTH Pool Sand - only used last season.



** Also - before anyone points it out - picture 6 does contain a lateral that doesn't appear to be properly seated - I wish this was my issue - but i ensured when I re-installed everything to tighten these more snugly this go round.
 

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Hey Texas - I actually mention this in the last sentence. I installed the laterals back on the standpipe assembly just for the picture to support so that I didn't have to take a picture of every single lateral for them. Sorry about that!


Its an Intex SX3000 - 16" Sand Filter w/ 3/4 hp pump.


I only filled my sand level to halfway up the standpipe this go, as I was thinking maybe filling to "Max" would do more harm than good.
 
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Its an Intex SX3000 - 16" Sand Filter w/ 3/4 hp pump.
Copy. I was looking at it from the position that "perhaps" your pump might be too strong for the filter, hence lifting sand up too high. But I don't think that is the case.
 
Your system is new, so if everything in the filter is as pristine as you describe, with no cracks or defects, then the only thing I come back to is the sand. While some pool sand brands have a bad reputation, HTH has usually been pretty good. Perhaps this is just one of those occasions where the batch of #20 wasn't quite up to par? If it continues without any other resolution, you might consider changing the sand one day to see if it makes a difference.
 
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Maybe you got some poorly sorted sand. Like you said, everything looks fine. There does look to be a fair bit of grains of sand that are about the size of the opening in the laterals. As much fun as it is digging out the sand from the filter, I would try a different brand of pool filter sand. I used Mystic White Pool Filter Sand from Ocean State Job Lot a few years ago and it has been fine.

I assume this only happen when filtering, not just after backwashing?

Is it possible that sand is getting in from the decking/patio around your pool? Before I redid the patio around mine the sand under and between the pavers would easily blow in or in hard rain get splashed/washed in.

I am a bit surprised to see the debris in the bottom of MPV, surprised it would act as screen. Looks like it catches debris but not easy to backwash out.
 
I appreciate the feedback. Regarding the quality of sand - I live in Michigan - and the "Do It Best" chain of stores around here offer HTH sand for $10 for 50lbs. Hoping its just because their pricing is good and not because they got defective batches. I had to purchase 3 bags, so if anything I would hope that not all 3 bags were bad unless all from the same batch. Also - wouldn't the bad sand have been cycled out by now after a whole season and some change?

Would a pair of pantyhose over the return line filter well enough to potentially "catch" sand so that I can 100% verify the sand is coming from the filter and not just from the air?


Bill - in regards to the question regarding the patio/deck - maybe but I highly doubt as I don't have any dirt roads or other usual suspects for putting a bunch of dirt in the air. Also - after vacuuming the pool floor still stays clear til the next day (after the pump has ran). I run my pump at night due to the chlorine degradation and also our energy supplier has some shiesty "peak energy use" rates. As far as the gunk in the MPV, i didn't realize this should raise any concerns.




One thing I didn't mention is - I did receive a replacement MPV from Intex. I haven't installed it yet, as I was wanting to try everything else before just slapping this new piece on there. As such, now that I've had the opportunity to narrow down possible suspects, can I just take off the old MPV and put the new one on or is there more to it? Also - if I do end up STILL having issues - Should I then focus my attention on the sand?


Thanks gents for the insight so far. Its greatly appreciated!
 
wouldn't the bad sand have been cycled out by now after a whole season and some change?
You would think so. Even after just a handful of backwashes.

Would a pair of pantyhose over the return line filter well enough to potentially "catch" sand so that I can 100% verify the sand is coming from the filter and not just from the air?
That should work. :goodjob:

can I just take off the old MPV and put the new one on or is there more to it?
If it's the same model and the plumbing lines will allow you to easily remove it, sure.
 
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