pump/filter sizing question

[riotejas]

Just waiting on the pebble sheen but I have a question about the equipment. I'm not sure my pool builder sized equip correctly and I would like some other opinions.
I have a 110' perimeter free form in ground w/ 8' spa. The pool has 4 returns and the spa has 9. Together the're about 27000 gals in volume. 2" plumbing.
On the pad I currently have a 2hp Hayward Tristar and a Hayward DE4820 filter. I've convinced the PB the pump is way to powerful and he's going to replace it with a 1-1/2hp Tristar. But I'm still afraid the DE filter is too small. The DE4820 handles 96gpm and the 1-1/2 tristar outputs about 130gpm

If the combo isn't right i have two choices:
1) Should I up the filter to a DE6020? or
2) drop the pump even further to a 1hp?

If #2 is the right answer, great, I'll run the filter cycle longer and it will also mean lower electric bills, but will that be enough gpm for all my returns?

How much does a gpm a return output? Somehow 12gpm pops into brain.

Thanks!!!

 

[JasonLion]

You might well need the 1 1/2 HP to run the spa jets but you won't want it all the time. The best solution is to get a two speed pump. Turn it on high to run the spa and on low to filter the pool.

A larger filter is *always* better.

 

[TheOne]

For a project/pool that large you should definitely consider a multi speed pump. To me it is worth spending the money for a better pump which gives you more long term flexibility. As JasonLion noted, you generally only need to turn your pump on high speed when you want alot of action in the spa or are doing a pool opening or heavy duty cleaning.

I turn on a supplemental air blower and put my filter pump on high speed when I want alot of spa action. Otherwise on regular filter mode it runs at a low speed.

FWIW my cart filter was intentionally "oversized". It can handle 150gpm although in my main filter mode I run my filter pump at 21GPM. I dont think there are many drawbacks to getting the larger filter. You would have a slightly larger DE requirement but you should be able to go longer between backwashings though. I am for paying a little more for less maintenance....

 

[mas985]

9 returns for spa? Is that 9 jets? With 9 jets you may need more than 2 HP. Also 2" plumbing for 9 jets seems too small as well.

A rule of thumb for spa jets is 15 GPM per jet so with 9 jets, that is 135 GPM! It is very unlikely that you will get that with 2 HP pump and 2" plumbing.

You may need to go up to 2.5 HP and 2.5" plumbing to get that. Perhaps even more.

You are right to worry about the filter since with a 2 HP, you may be pushing well over 100 GPM.

Also, you may want to consider a two speed pump or two separate pumps for the spa jets and circulation. That way you can dimension each pump for the job.