Why don't PB's plumb water heater to spa side only?

[mgianzero]

I own an in-ground pool which has a pump for the pool (inline with filter and SWG) which can be switched to run 4 jets in the pool with or without the gas heater. My other 8 jets use a separate pump system which merely circulates the spa.

With our concern for efficiency these days, why does every PB run the same water heater which can be designated for either pool or spa circulation? I never want to heat my pool with gas, it would cost a fortune! I only want to heat my spa.

But all PB's seem to design it this way. I've heard from some "experts" that it's always good to circulate some water through the heater at all times. But why? It takes more plumbing and higher resistance to flow through a heater. Why not take it out of circuit when I'm circulating only for my pool?


Marc

 

[jblizzle]

Because the water needs to be filtered before the heater.

You could plumb in a bypass around the heater so the flow does not go through it when you do not want it to.

 

[Richard320]

I'm assuming it's a spillover spa and you have valving that splits suction and return for pool and spa to the filter & heater? That's the way mine is set up, along with a booster pump that just works the spa, no heat.

I have been known to nudge the pool temperature a couple degrees when we were expecting company. But otherwise, I'm with you, heater only works on the spa. I'm such a cheapskate I suck a couple inches out of the spa beforehand to allow for displacement when we get in. Why heat it just to have it spill out into the pool immediately? I also don't run the spa booster because that just chills the water I just heated. For the same reason, I cap the air intake on the spa venturi so there's no cold air being introduced into my expensively-heated water.