zodiac lm2 clear water

Hi Marko, and welcome!

If a cartridge is big enough it CAN hold the debris of a season, but usually our members have to clean it more often than that, and it can be one of the messiest jobs in the world. People who have cartridge filters generally fall into two groups: Those that LOVE their cart because of the low maintenance, and those that hate it and go to bed every night cursing the builder for talking them into it.

The first group have figured out there ARE ways to clean the element that are much easier, some even keep two, to swap. I gather soaking it in a plastic garbage can with electric dishwasher detergent can be very effective and make it much easier. The thing is, if you do NOT learn all the tricks (and I don't know them all), cleaning will be a messy job that takes a couple of hours or more.

Another thing: IF you get a problem and need to vacuum your pool and need to send the debris to waste (drain or gutter), most cart filters don't seem to be plumbed to allow you to bypass the filter and send the water to the sewer system.

But builders LOVE carts because the user expects to go the season without maintenance, and....then the 1 year warranty on the install is done and where are you?

Also, pool sellers LOVE to push horse power on pumps. This creates two problems:
1) Bigger pumps don't necessarily do a better job, but DO consume excessive electricity. Your pool will be about 8500 gallons. You absolutely do NOT need a pump bigger than 1/2 to 3/4 hp. A 1 or 1.5hp will be a waste. Sellers push bigger
pumps because their incremental cost between a 3/4 and 1.5 is very little but the MARKUP is big. It seems to be an "upgrade" but it's not. Watermom, one of our moderators, uses a 1/2 hp pump on a far bigger pool.
2) FAR MORE IMPORTANT!!!!! If your pump's output in gallons per minute exceeds your filter's maximum rated gallons per minute it will NEVER filter properly and frequently will damage the filter. Bad, very bad, yet it happens all the time. And, if the filter is damaged due to an oversized pump, the manufacturer of the filter won't honor the warranty. So if you go with a cart, do not accept it unless the builder can SHOW you in the specs that the pump doesn't exceed the filter's capacity.
Further, most filters don't seem to do as well when they are running at maximum capacity, but do better when they are getting a lower flow rate. My sand filter, for example, actually gets the water cleaner when it's running at low speed rather than high speed (I have a two speed filter).

The problem of too-big pumps is common. Your two other choices of filter are DE, which filters extremely well but is a little more complicated to maintain, requiring the addition of DE powder regularly, and sand, which is what all of the moderators use. Sand is much lower maintenance than DE but higher maintenance than a cart...but you don't have the messy element cleaning. Also, you never need to replace the sand.

A lot of times manufacturers package pumps and filters as a unit, from very tiny to fairly large. USUALLY this is OK because the manufacturer, like Hayward or Pentair is selling them as a unit and the pump shouldn't be too big for the filter. I don't know if they do it with carts but they do bundle sand and DE filters.

Before you commit to anything, I'd go to our sister site, PoolSolutions.com and explore. Especially look at the tip on the bigger pump scam. The recommended models in the article may be out of date (I don't know if Ben, aka, PoolDoc updated them) as the original article is over 10 years old but is still absolutely valid today.

There is no "best" filter system and there is no free lunch. Every filter system, if sized and set up correctly, and if properly maintained, can do the job perfectly well, giving you clean, crystal water. Each has its advantages and drawbacks.
1) DE filters best, nominally, but are fairly high maintenance. DE powder isn't expensive, and parts only need replacement if worn out or damaged.
2) Carts filter next best, seem low maint, but cleaning elements is, for most people, a nightmare. Replacement elements are extremely expensive and can be damaged during cleaning
3) Sand filters the worst, but with some simple, inexpensive tricks, can do as well as the others. But sand filters are heavy, so you can't put them away for the winter, and require frequent, albeit easy maintenance. Unless parts are damaged or worn out, there's nothing to replace in a sand filter as the sand lasts at least as long as the filter.

Carl