Calcium Hardness in Manfufactured Spa

[rob.mwpropane]

I was reading trying to dial in my spa chemistry and need some clarification. I have a Hawkeye Spa (I think). It is a fiberglass shell. In the sticky at the top of this sub forum it says CH 130-150, but the fiberglass pool section states 220-320?

I don't believe my spa has a "gelcoat" as there's nothing shiny about it. I'm just not sure what level to keep it at. Right now, I'm around 75. Instinct tells me follow the sticky and shoot for 130-150?

 

[JoyfulNoise]

The main purpose of CH in a spa is to reduce the tendency of oils and organics to form foams. 150ppm CH seems to be a good balance between foam inhibition and saturation index for a spa. The main drawback of high calcium hardness levels is that it eventually leads to scale formation inside the heater which reduces heater efficiency and eventually leads to heater failure.

The sticky’s recommended levels tries to balance those two extremes as much as possible.

 

[mknauss]

A CH of 130-150 is simply to prevent foaming. If you are not seeing foaming at 75, you do not need to raise it further.

Take care.

 

[rob.mwpropane]

The main purpose of CH in a spa is to reduce the tendency of oils and organics to form foams. 150ppm CH seems to be a good balance between foam inhibition and saturation index for a spa. The main drawback of high calcium hardness levels is that it eventually leads to scale formation inside the heater which reduces heater efficiency and eventually leads to heater failure.

The sticky’s recommended levels tries to balance those two extremes as much as possible.

As per the sticky;
"The lower your CH, the higher your TA and pH need to be to have balanced water. The higher your CH, the lower your TA and pH need to be."

So CH does have an effect on TA and pH? Should I raise from 75 to 140?

I see some foam, but not much.

I do not use the spa heater. It is 100% disconnected underneath. I have everything plumbed back to a 400K pool heater, so no real worry about scale (unless I still need to be worried about the pool heater and scale?)




Thanks for everyone's responses.

 

[mknauss]

Though somewhat true - the real thing to monitor is CSI. CH, TA, and pH are the primary drivers of the CSI. With a fiberglass pool your only real concern is scaling. And I can guarantee if your CH is below 100 and TA below 100, with pH in the 7's, you have no issues. PoolMath will calculate CSI for you.

If you are seeing foam, raise your CH to 100. See how that works.

 

[rob.mwpropane]

Though somewhat true - the real thing to monitor is CSI. CH, TA, and pH are the primary drivers of the CSI. With a fiberglass pool your only real concern is scaling. And I can guarantee if your CH is below 100 and TA below 100, with pH in the 7's, you have no issues. PoolMath will calculate CSI for you.

If you are seeing foam, raise your CH to 100. See how that works.

Thank you Sir, will do.