What size of new filter to get - getting different answers

My current 300 lb sand filter bit the dust. I have a 1hp pump, an in ground pool, with around 18000 gal (I think - it's a kidney shaped pool and don't have complete confidence with that estimation).

I am getting differing information from various pool companies on what to replace it with. I think I'm going with a cartridge filter but one company recommends a 420 and the other a 520 filter. Another company recommends sand and says it's my call whether to go with a 300lb or 500lb. I am looking for advice on what size cartridge filter I need - I don't feel like any of the companies are taking the effort to look at exactly what I need. I have lurked around here a bit in the past and have found the information very useful. Thank you.

Sand filters are easiest, and over-sized sand filters perform exceedingly well.

DE filters are higher maintenance but give visibly better water quality (*CRYSTAL* clear)

I'll let other folks tell you about cartridge filters; they like them -- I usually don't.

What does "bit the dust" mean? Does it mean the multivalve is broken, or the laterals inside? Or does it mean the basic tank is irreparably damaged?

If it's the laterals, you'll need a new set and 300# of sand.

If it's the multivalve (assuming it's not fixable), you'll need that.

If it's the tank itself, you are probably right and a new one is in order.

Carl

It split - 2 inch split down the side of the tank.

Any thought on the approximate size of cartridge filter that I need?

Here's Pentair's page for one of their cartridge filters:
http://www.pentairpool.com/pool-owne...filters-28.htm

Click on the "specs" tab, to match a filter to your pool volume and water flow. It looks like the smallest one would be within specs on your pool. But, with cartridge filters, there's no downside that I know of to oversizing them, and you'll be able to go longer between cleaning with an oversized filter.

Thanks!
So the last pool guy I talked to (who was recommended) is proposing a Pentair 520. That sounds massive. Is that just way too big???

Can anyone say if Pentair 520 is way too big for my pool? I have to have a decision by morning and have no clue.

Thanks!!