I’m looking at replacing my existing 1 ½ HP single speed pump with a 2 speed. I just need a little help on calculating what size I should get and the total head of my system.
I have a 15,000 gallon in ground pool with spillover spa and 1.5” piping. I calculated that I need a 30 GPM pump for a full turnover in 8 hours. My problem is I’m not sure how much head I have in my system. I can fairly easily calculate it out but I’m not sure what some of the check valves in my system are adding. I currently have 2 spring check valves in the system and then another one in my heat pump (which I could put in a bypass valve to completely bypass it since it’s only used when using the spa). One of the two is after my filter because I have a solar system on my 1 story patio roof (about 10’ up) and the 2nd is on the spa return line so the spa doesn’t drain down to the level of that return when the pump is turned off. I can replace the one at the pump with a flapper type if I need to but the one for the spa is in a vertical position and would need to stay as a spring type.
In doing the reading I’ve done so far on 2 speed pumps, I’m thinking I might be able to get away with running my new 2 speed pump on low all the time, and then flip it to high when running the spa. This situation would be ideal because I wouldn’t have to add any additional controls for the pump. I have a Zodiac MX8 cleaner which says it can run on as low as 20 GPM, which is well under my required 30 for my water turnover. So based on whatever my total head is, if I could find a pump that met that requirement at 30 GPM on low speed I’d be a happy camper.
It also appears as though since the solar system is only on the 1st story that a pump on low speed should have enough power to purge the panels.
Am I headed down the right path or totally crazy? What should I add for the spring check valves in my system? Would running the pool cleaner on low be effective and is it doable?
Here's a picture of my system if that helps...