What filter to choose...cartridge or DE

[waterbear]

DE filter owner here.... man, now I'm all worried about this silacosis thing.
Just use commen sense and don't breathe the stuff. The risk of silicosis from DE power is very small but also very real. (and so are the dangers of working with muratic acid and chlorine! Just use commen sense!)

So... what cartridge filter would you recommend for a 35,000 gallon pool (one pool guy told me it's 40,000) with a 1 hp. pump?
Cartridge filters have a maximum gpm residential flow rate. You want to be well below that. For commercial pools the maximun flow rate is .375 gpm/sq. ft. of filter area which is much lower than the maximum flow the filter can handle. You want to be closer to that flow rate. You need to calculate the flow rate from your pump based on the performance graph and find the biggest filter that will operate at that flow rate or slighly higher. This will be a much larger filter than if you went by the residential rating. For example, my pool would only need a 75 sq. ft. filter accoring to my pump size and the residential maximum flow rate but my builder put in a 150 sq. ft. filter which my pump can handle fine also (my pump had to be larger because of the spa than if I only had a pool. If I didn't have the spa I would have had a smaller pump and would only have needed a 50 sq. ft. filter, which, in fact, one builder used in a proposal with a separate filter system for the spa when I was shopping for a pool) If he had gone with the smaller one I would have a much shorter filter run time (time between cleanings) than I do and would probably hate my cartridge filter.
Thanks,

Ilan

I know this is a bit confusing but it is the best answer I can give. Sizing a pump and filter is a bit tricky. General rule of thumb for a cart. is get the largest sq. ft. your pump and plumbing can handle efficiently.