Re: which DE filter to buy??
I have a 22K IG pool with spillover spa, two returns, two main drains and 1 skimmer. I have a 1 1/2 HP pump with 48 Sq Ft DE Pro Grid Hayward Filter and 1.5 inch lines. I did not pick out or buy the filter but the pro grid is real easy to open (loosen metal belt/clasp around the side) and then remove filter 'fingers'. I am not sure of the cost but I think it was > $600.
Re: which DE filter to buy??
Not sure how well it will work yet since they're just building the pool, but pentair has a 100sf DE filter (Quad 100) in a cartridge design that should reduce the frequency of backwashing and cleaning pretty well. I'm pretty sure the only risk you have is buying one too small, otherwise it's all about surface area (well, and ease of cleaning, quality, etc) and the larger the surface area the less frequently it'll need to be cleaned. Of course it'll also use more DE when backwashing but my goal was to stretch the intervals out as much as possible.
Re: which DE filter to buy??
Two months ago I installed a hayward pro grid 36 sqft de filter; I was replacing my old hayward sand filter. The pool has three returns, two skimmers, a main drain, a slide return, and a whisperflow 1 hp pump, 2" main piping.
With the sand filter the pressure would start at 20+ psi after backwashing but the 36 sqft de filter starts at 10 psi. During two months the de filter has been in operation the pressure has risen 1 psi. At this rate the filter will only have to be backwashed/cleaned once a season.
I was afraid of buying filter to small but so far the 36 sqft is doing great and the water flow in the pool is much stronger. Now the kids can swim in place against any of the return currents. Same pump same piping only the filter has changed and it made a very noticeable difference in flow.
Re: which DE filter to buy??
I'd be really interested to know which is the most popular brand too. IS bigger always better with DE?