Lots of sand in pool - from water feature...

Okay, here’s the deal. Bought the house with pool already installed. Including a ‘grotto’ at the deep end. The grotto is sandstone with a big slab of sandstone over the top. The problem? The pool builder used stone that is REALLY soft, that is, it sheds fine grit and flakes constantly. The Dolphin pool cleaner picks up a healthy handful every time I run it, no matter how often - back to back cleanings, same result. Plus the Dolphin stirs up the sand, so it’s cloudy for hours. Sand builds up on the splash pad and seats within hours of vacuuming. Grrr…

New cartridge filter system last year. The sand got old, then the upper housing cracked, so it was ready to replace.

I’m considering adding a separate bypass filter to filter out the smaller/tiny grit - like 5-10 microns. At a previous house I added 20" tall water-filter housings for whole-house filtration, one for sediment and one with charcoal. Seemed to help. Anyway, I screwed up and bought the wrong size filters, so I have two HUGE filters, 20" long but 4-1/4" diameter. Cheap enough they weren’t worth returning.

Now, I’m thinking about buying the correct size filter housing, and plumbing this extra filter to catch the really fine stuff. The big housing is under $65 with no filter included - McMaster-Carr.
Obviously it can’t take the GPM of the whole system, but plumbed in bypass maybe 5-10% of the water would go through it. Over time it should catch the fine stuff the big cartridges won’t.
Thoughts? The only other solution is to tear out the grotto and rebuild it with better stone. The house is some kind of sandstone too, but it holds up just fine. This stuff is so soft a garden hose creates a river of reddish silt. Ugh.
Thanks!
c.

Hi CCrider147,

What a headache! I like your idea of the bypass filter, I would try this first! If that doesn’t work then maybe go with a DE filter for the by-pass filter as that will filter down to 2 microns. Also on the dolphin are you using a bag or a cartridge on the inside of the cleaner? If you are using a bag then if you could let me know the model of the Dolphin cleaner then I could check to see if there is a cartridge upgrade kit available as the cartridge will filter smaller debris than the bag.

Thank youPatrick!
The builder cheaped out on the stone - so frustrating. The Dolphin is a ‘Triton’, uses four panel filters. Originals are pleated, replacements are a thin membrane. Both work pretty well. We also have a Polaris that came with the pool, it works better with leaves (oak trees) but not so much with sand.

Thanks for validating my bypass idea. I have a bag of cellulose fiber, bought when the sand filter started going out. But i don’t want to clog the main cartridges - I understand DE/cellulose is not recommended for cartridges (?)

I’m going to order the filter housing and plumb it in. Not expensive, and can’t hurt anything. This is the unit I’m looking at: McMaster-Carr
With 1-1/2" inlet/outlet, it should flow pretty well. McMaster has filters down to 1 micron (!!)

Thanks again for the reply - I’m interested in finer-filtering panels for the Dolphin too. And I’m going to go shopping on your site…
Thank you!
chris

Hi Chris,

Thanks for the follow-up! Just make sure to only divert a small amount of water to that filter as it can only handle 20 GPM and if you go higher than that then it could damage your filter and pump.

If the by-pass doesn’t work then you may want to replace your main Pool sand filter (20-40 micron filtering ability) with the biggest & badest DE filter (2-4 micron filtering capacity), something like this 60 Sq. Ft. FNS Plus DE Filter and this 2" Slide Valve for FNS Plus.

Patrick,
The new filter is a Pentair cartridge unit, not sand/DE. Just as I was researching upgraded ‘sand’, the top housing cracked, so I had to buy a whole new filter unit anyway.

Totally understand diverting a portion of water, not 100%. Some oil and coolant filter systems work similarly - they filter maybe 25% on any one pass, but over time they get it done.

Don’t need new cartridges yet, but planning to buy an extra set to minimize downtime. Too many options - I’ll have to spend some time on your site…
Thanks!

Good luck Chris, keep us posted!