Filter replacement options
We purchased the house this winter; the pool was closed by a local company who cleaned the filters; upon opening the pool this year the PSI was at 12. I spent 3 hours yesterday cleaning the filters (hose with regular spray nozzle) for the first time after the PSI reached 23, and after putting them back in the PSI only dropped to 16. They could probably be improved with the overnight soaking, but theyíre looking pretty worn overall and so Iím looking to replace them after the end of the season.
I found replacement filters for about $430, but am considering switching to sand or DE; leaning toward sand if I do switch. Iím trying to figure long-term cost and canít seem to find clear data on how often DE needs to be cleaned/replaced and how often the grids would likely need to be replaced (and the cost to do so). It looks like sand lasts about the same amount of time as cartridges, if not longer, and is $30-$50 to replace vs. $400+ for cartridges, so definitely cheaper long-term.
I found some sand filter calculations, and at about 40K gallon Iím looking at 83 GPM or a 5.5 sq ft filter. I looked around a bit and I think maybe the Hayward S310T2 at just over $600 might fit the bill. Does that sound right? Any other recommendations?
Pool and equipment specs are in my signature, but for some additional info, the main drain and one skimmer are sealed, so there are only two working skimmers and 3 jets. We have a robot vacuum that I run 2-3 times per week, which is probably more than is needed because we have an auto-cover that stays closed when not in use, so overall the pool stays pretty clean. Currently use chlorine tablets but will switch to bleach once I run out of the original stockpile (before the end of the season). Strongly considering adding a SWG, but will do some kind of automation if not. Will likely replace the pump with variable speed, but not until the current pump dies (and it seems to be working fine); we run the pump 24/7.
My main reservation about a sand filter is the filtering capability. I really like the pool to be crystal clear and sand only gets down to 20-40 microns, but if the human eye can only see as small as 50, how much does it matter? I also understand youíre losing water with the backwash, but about how much (in terms of gallons)? We have well, so I do fill using the hose-attached filters, so thereíd be some extra cost to purchase those for the fill water.
Thoughts or suggestions?