Replacing cartridge with sand

The usual rule for backwashing a sand filter is when the pressure goes up at least 5 lbs. I'd guess it'd be the same for cleaning carts.

let me say the filters are the same size that cane with the pool. I have never changed the size. I have 4 cartridges that barely fit in the housing so there is no room for bigger. I only clean about 2-3 times a year. Im going to clean them with cleaner and wash completely. My filters are Unicel, so no cheapies there. I'm hoping by through cleaning each time it will get better

5 PSI is over 11' of extra head which can significantly reduce flow rate in a pump no mater what filter type. For example, with your pump (Carl), if your normal operating point is 54 GPM @ 40' of head, at 50' of head, the flow rate would drop to 40 GPM going from 50' of head to 60' of drops it to 9 GPM! Personally, I would not let the filter pressure rise more than about 25% of the clean pressure to keep flow rates up. But then again, if that meant backwashing every week, I might stretch that.

Dansdad,

My size comment was regarding kelmvor's comments. But is sounds like you have fairly large filters.

Thanks got responding I think I just need to replace my filters as there are two from the original setup and pool is 7 years old. I'll start fresh with new filters and then keep them clean

I have two sets. I use the old set for opening and change it out after two weeks. Then my good set lasts about 2 months.

does everyone s cartridge filters last before being replaced? one season? 2 years? I'm really wondering

I have one set of cartridges going on 9 years now.

The only reason you should need to replace your cartridges is because they are torn which is often caused by cleaning or they are so clogged that you cannot clean them anymore which is often caused by bad chemistry. So the key to extending the life of the cartridge is keep the chemistry in balance and avoid algae blooms (I have had one in 9 years), and go with a large filter to minimize cleaning and the chance of damage. Also, a small pump helps to reduce the flow rate through the cartridge filter.

thank you ...im getting a plethora of info here