Just to start off on the right foot - I know the Pool Forum is mainly about pools and I know that pool water chemistry and spa water chemistry are different beasts. That being said, I'm sure there's a subset of PF'ers that, like me, have pools with attached spas. So if this thread is not in the right Forum, feel free to move it.


So our pool has an attached spa that we like to use on occasions. The way our plumbing and automation works (and I think this is fairly standard) is that we have three returns to the pool and one return to the spa (aside from the five spa jets that only operate when the plumbing is in spa mode). I can split the return water between the pool returns and spa returns and typically leave it at 50/50 so that the spillway water feature runs. I plan to automate that three-way valve someday soon so I can better control my water feature.

All the above means is that the pool water and spa water start off with the same chemical balance. I typically try to achieve the following chemical ranges and I'm almost always in these ranges -

FC 5-7ppm
pH 7.6-7.8
CYA 50-70ppm (current value is 70ppm)
TA 70-90ppm
CH - 550ppm (current value)
Salt - ~4000ppm (current value)
Borates ~ 50ppm (current value)

The spa is 650 gallons and when I run it, I typically find 95F to be a very comfortable temperature. The IntelliFlo is set to it's highest speed and there is no booster pump, just a Venturi air draw to make the bubbles. The IntelliChlor auto-magically switches over to Spa-mode output which is around 2% power (max is 5% in spa mode).

So here are the questions -

1. What would be optimal spa water pH and TA to achieve prior to getting in the spa?

2. Is it better to bump up the FC prior to going in or afterwards?

3. Is there anything else I'm missing?

In the past, I would just run the spa with the water balance as-is and then return the system to pool mode and let all the spa water spill over into the pool. I know from measuring the spa water after use that the pH is typically quite high and the CC's are up from the bather load (I think I can actually smell the chloramines) and I imagine the TA is probably quite low from CO2 outgassing. The spa volume is only a small fraction of the pool volume (16,000 gallons) but I don't like dumping waste water into my typically sparkly pool.

Any advice or pointers others might have would be most appreciated.