Hi Watermom, thank you for the reply.
I tried posting an answer but I can't see it yet, maybe because of moderation.

We measured the pool, it is 20k gallons: 19k and some for the pool and over 750 gallons for the spa, but the water is on the same system.

The filter is the CCP420 Pentair: http://www.amazon.com/Pentair-CCP420.../dp/B007E4W5VM
Booster pump: Pentair LA01N http://www.amazon.com/Pentair-LA01N-.../dp/B0039POBW6
Pump SQ1152L which might be this one: http://www.amazon.com/DynaGlas-Pump-.../dp/B00A4MX99S