"docjohnson" wrote in message oups.com...
I have a 12,000 gallon in-ground pool with a spill-over spa. The pump
that is currently installed is a 3/4 hp Sta-Rite. The filter is a
cartridge type. I also have a heatpump in the system. When I have the
heat pump in-line, I cannot get the jets in the spa to suck air down
their vents to produce bubbles. The only way I can get the jets to
produce bubbles is to by-pass the heat pump and open all the return
drains from the pool to the pump but that cools off the spa. I
eventually would like to install solar panels on my 2 story house. I
have a feeling the pump is undersized, but shall I go 1hp or 1.5hp?
Will I need to get a bigger filter for the larger pump? Pressure into
the filter is 10psi with the heater bypasses and 19 with the pump
in-line.

I would not be surprised that if the heat pump installation was designed to limit flow
so as to get the temp up to spa temps when heating. If it is drawing the water from the
pool, it has to heat the water a lot to get it up to temp. You could use a return from the
spa, and another pump, or a bypass with most of the water coming from the spa. If you
draw the same amount of water from the pool as it does now, with the rest coming from
the spa, your temps should hold better. You would lose some efficiency because the
heat pump would not be able to supply as much heat to spa temp water as it can
to pool temp water, so you'd probably want to switch it back to full pool water supply
when you aren't using the spa.

Bob