Needing new filter system, confused!!!

[Chief2505]

Last fall due to human error I damaged my sand filter and now I need to replace it. I have spent hours researching and pricing different types and sizes of filters and had pretty much decided to go with a 425 sq ft cartridge filter instead of the sand filter.
I was ready to pull the plug and order one when I came across an article about making sure your pump is not too big for your filter! That through me into more research and more reading. And more confusion!!
Through my reading here I know the more filter area the better, I have also come to the conclusion that cartridge is better than sand.
So by my calculations, my pool is 36,000 gallons inground, I have a single speed 1.65 HP 3,450 RPM pump and I have two 1 1/2" inlets coming to the pump. My research says that my max flow rate is 84 GPM due to pipe size. I generally run my pump 12 hours a day with a timer controlling the on and off of the pump. I use a robot nautilus CC plus every day to vac and once a month or so I will manually vacuum as well.
After all of this, my question for help is......can I install the 425 sq ft cartridge filter that has a 110GPM rating with my existing pump and be ok? Also, how do you vac to waste with a cartridge system? Or should I just go back to my 24" sand filter with 300# of sand that I know works well with my existing pump?
Thank you so much.

 

[Texas Splash]

can I install the 425 sq ft cartridge filter that has a 110GPM rating with my existing pump and be ok?

I'm not seeing any issue? What about you @mas985?

how do you vac to waste with a cartridge system?

You don't UNLESS you add a spigot or 3-way valve right after the pump and before the filter. That way you can open it up while the pump is running to let water go out to waste.

 

[mas985]

So by my calculations, my pool is 36,000 gallons inground, I have a single speed 1.65 HP 3,450 RPM pump and I have two 1 1/2" inlets coming to the pump. My research says that my max flow rate is 84 GPM due to pipe size.

Pipe size alone does not limit flow rate. Those are recommendations, not limits. With a large enough pump, theoretically, there is no limit to flow rate.

With your current pump on your current plumbing, the operating point is fixed to a specific value but that could be more or less than 84 GPM and more than likely it is less than 84 GPM.

After all of this, my question for help is......can I install the 425 sq ft cartridge filter that has a 110GPM rating with my existing pump and be ok?

Yes, that should be fine but most 425 sq-ft filters have ratings of 150 GPM. What is the make/model for the filter?

Also, how do you vac to waste with a cartridge system?

You install a 3-way value with a discharge pipe before the filter.

 

[Chief2505]

Pipe size alone does not limit flow rate. Those are recommendations, not limits. With a large enough pump, theoretically, there is no limit to flow rate.

With your current pump on your current plumbing, the operating point is fixed to a specific value but that could be more or less than 84 GPM and more than likely it is less than 84 GPM.


Yes, that should be fine but most 425 sq-ft filters have ratings of 150 GPM. What is the make/model for the filter?


You install a 3-way value with a discharge pipe before the filter.

I am considering the Doheny Deluxe Cartridge and it is rated at 110 GPM.

 

[1poolman1]

These numbers allow the recommended no-more-than 7 feet per second flow. You can push more water through.