Does CH matter at all in a vinyl pool? What about for heater or SWCG?

[wayner]

I was having this discussion and I read on Pool School here where it says that for vinyl pools then CH doesn't matter. But they insisted that it did matter if you have a heater. I would think that with a heater or SWCG that lower calcuium means less limescale buildup.

Anyone know the answer?

Here is the quote I was referring to - under Calcium Hardness on ABC's of Pool Water Chemistry

In a vinyl liner pool there is no need for calcium, though high levels >650 ppm can still cause problems.

 

[ajw22]

Some scale buildup is desired in a gas heater to protect the heat exchanger.

The CSI is different for the same water chemistry when in the pool, the heat exchanger, or the SWG.

So you get the desired scale in the heater and not in the pool or SWG.

Calcium Hardness - Further Reading

www.troublefreepool.com

 

[wayner]

Thanks for that. My water tends to have CH around 120 so I will try to up it a bit next year.

 

[JoyfulNoise]

Thanks for that. My water tends to have CH around 120 so I will try to up it a bit next year.

I really wouldn’t bother doing that. The “scale” layer in a heat exchanger isn’t necessary when it comes to pool water because your pool water is rarely, or SHOILD RARELY BE, acidic in nature. Scale in heat exchangers is what I like to call “borrowed science” - it makes sense in closed loop water boilers and steam generators, but absolutely no sense in an open pool with highly mineralized water. These types of “borrowed wisdoms” are what you get when you confuse “science” with “engineering”.

Unless you’re planning on running demineralized and acidic water through your pool heater, don’t bother adjusting your CH upwards. You’ll do far more potential damage to your SWG cell by messing with calcium levels than any perceived good you will do with your heat exchanger.

 

[wayner]

Thanks @JoyfulNoise - that's the way I have thought about it ever since I owned the pool, but I kept hearing about needing some CH. I did have to replace one heater, but it lasted about 12 years. The current heater was installed in May 2019 and seems in good shape.

 

[JoyfulNoise]

Thanks @JoyfulNoise - that's the way I have thought about it ever since I owned the pool, but I kept hearing about needing some CH. I did have to replace one heater, but it lasted about 12 years. The current heater was installed in May 2019 and seems in good shape.

Pool stores like to claim that because calcium carbonate is used in the manufacturing of liners as a white coloring agent and to modify the mechanical properties of the vinyl to make it easier to manufacture into sheets is all the reason why you need higher calcium levels. They claim that leaching calcium out of liners will make them brittle. There simply is no good evidence of this nor is there even any widely accepted literature on the subject within the industry that makes vinyl sheet starting materials. Pool liner manufacturers will occasionally use sheets of vinyl from multiple different raw material vendors without ever disclosing that to the end user. So there’s really no hard or fast rule on how much CH is actually needed. We do know that chlorine and pH contribute to much more potential damage than any other chemical level. So it’s really not an issue.

Simply keep CH levels in a range that is easy to manage given your water sources and don’t stress over them. It’s by the least important parameter in a vinyl pool.