Low TA, High CH required?

[Chakara]

I've had this spa a little over 2 years. My TA runs around 35 to maintain a good PH around 7.6. Of course on poolcalc my CSI is kinda far into the negative - around -4.

The water starts with a CH of around 80 and I've always just bumped it to 150 and left it there, but now I'm wondering if I shouldn't raise the CH to around 300 - which should give me a CSI of near 0.

So I'm just looking for a sanity check - does this plan make since?

Thanks all!

-Chak

 

[JasonLion]

There is no point in taking CSI all the way up to zero. If you really meant -4.0 then yes that is way to low, but -0.4 is fine.

The recommended CH level for fiberglass is 220 to 320. In fiberglass it doesn't make nearly as much difference as it does with plaster, but it can help the gel coat last longer.

 

[Chakara]

Cool - it does say the -.6 is indicative of problems - but not for fiberglass, just stone based linings.

That said, if 220-320 is best for fiberglass, then perhaps I should go for the CH of 300.

I have to be honest - I don't think the material is fiberglass, but its definitively man made.

On a side note, I don't use Borates and I don't like them. It makes the bubbles pop/splash my face. I'm also trying this fill with no CYA's just to see how things go.

 

[JamesW]

If the tub is fiberglass, then the CSI does help. However, if your tub's surface is acrylic, then you really don't need to worry about the CSI.

Going to 300 on the calcium would most likely scale the heater.

 

[Chakara]

Ok, so is there a downside to higher CH? I realize a lot of people aren't lucky like me in having a fairly low CH water source.

I would guess it is acrylic - there is a 1/8" thick colored textured layer of what looks like plastic over a white/gray base of about 3/8" thickness.

 

[JamesW]

Ok, so is there a downside to higher CH?

The water temperature in the heater can be substantially hotter than the rest of the water, which increases the CSI in the heater. Increasing the calcium to 300 would risk calcium scaling damaging the heater.

 

[Chakara]

Cool - then a CSI of -0.4 with a CH of 150 it shall be. Does make me wonder if I should leave my CH at the fill water level of 80 though, but running in the calc, even if the heater is at 200 degrees (much more and it would boil the water), my CSI is @ .36 - so it swings from -0.3.x to +0.3.x - IE: perfect

Thanks for the feedback guys!

-Chak

 

[chem geek]

The temperature of the heat exchanger water pipe in the heater is probably around 30ºF hotter than the spa water, so perhaps 134ºF or so.

 

[JamesW]

If the heater is an electric element, it will radiate about 5,000 watts. I'm not sure how hot it gets, but it will get quite hot.

 

[Chakara]

Hm - I can see where the element would get quite hot - but it also has a fair amount of flow over it. I would think that at the very surface of the heater element would be much hotter than even .1 inches away.

I don't know if the spa pack runs the water for a while after it turns off the heating element - as that could be another factor.

All said, I think I'll be OK with a -0.3x CSI. Unless one of you guru's think it is wiser to have a higher CH, for a lower CSI.

-Chak

PS: once again, thank you all for this site and your advice. I don't know how people survived before the internet