Attached SPA impact on Pool Chemistry

Esloser

Well-known member
Jun 23, 2016
513
Millville, NJ
Just curious... how does an attached SPA impact the rest of the pool's chemistry. I have a 6 jet attached spa that overflows into the pool when not in SPA Mode. I'm wondering how it impacts the pool chemistry - PH, FC, etc. with the water getting heated to 94-100 degrees and blowing air through it.

Eric
 

foobert

LifeTime Supporter
Jul 19, 2013
143
Bay Area, CA
Aeration will tend to raise you PH.

Temperature has a minor effect on CSI values (you can see change in the Pool Math). Othewise, it's not much different than having well used and splashed in pool.
 

Esloser

Well-known member
Jun 23, 2016
513
Millville, NJ
I guess that helps explain why I go through so much Muriatic Acid - usually 2-3 gallons per week. It's also a new pool, so I have that working against me too. What about FC? Does warmer water use FC faster than the cooler water of the pool?
 

Richard320

TFP Expert
LifeTime Supporter
Jan 6, 2010
20,796
San Dimas, CA (LA County)
I guess that helps explain why I go through so much Muriatic Acid - usually 2-3 gallons per week. It's also a new pool, so I have that working against me too. What about FC? Does warmer water use FC faster than the cooler water of the pool?
I couldn't say for sure. I only run the heater when I'm using the spa, and then I only heat the spa. A spa-load of water at 100 is only going to raise the rest of the pool 1 or 2 degrees. Not enough change to make a noticeable change in FC, I doubt.

When I use the spa, I start my drawing the water down a few inches, so that when we get in, it doesn't overflow. Why heat it just to push it out? Then I set it to spa only and fire up the heat. There's less water to heat since it's already been lowered. Heats faster. I also don't like the blower and I restricted the air intake to the venturis. Why heat water and then blow cold air in it to cool it off? When we're done, I kill the heater and switch the valves and let it fill and spill out.
 

Esloser

Well-known member
Jun 23, 2016
513
Millville, NJ
Do you draw from the pool at all when using the Spa? I was thinking of cracking open the pool suction line to pool a little bit of pool water into the spa to trickle it over the spillway. That way, if someone gets out, the spa will slowly return to the right water level. I haven't tested my theory yet.
 

Richard320

TFP Expert
LifeTime Supporter
Jan 6, 2010
20,796
San Dimas, CA (LA County)
There's only the two of us that use the spa, so an inch or so is no big deal. When I have the heat on in the spa, I only want to heat the water in the spa and no other. Drawing from a cooler pool will just chill the spa.
 

windyknollsva

New member
Jun 29, 2016
4
Berryville VA
I too have attached spa. Last time we used spa legs itched. Here are my numbers.
Unheated FC 5 PH 7.4 TA 90
Heated to 99° FC 5 PH 8.0 TA 90
How low can I keep the PH in my pool so the heated spa PH is not so high?
 

Richard320

TFP Expert
LifeTime Supporter
Jan 6, 2010
20,796
San Dimas, CA (LA County)
I too have attached spa. Last time we used spa legs itched. Here are my numbers.
Unheated FC 5 PH 7.4 TA 90
Heated to 99° FC 5 PH 8.0 TA 90
How low can I keep the PH in my pool so the heated spa PH is not so high?
It's not the heat. Heating the water should lower pH PH levels

The spa is probably churning with bubbles and aeration drives the pH up. When I attacked my high pH with acid & aeration, I let the spa run full bore and drove the whole pool's pH up from 7.2 to 7.6 in about 4 hours. You might find that lowering the TA in the whole system will slow the pH rise in the spa. I don't care much for all the froth and I don't see any point in heating the water only to cool with cold air, so I don' run the blower and covered the venturi intake so I just get hot water.