Considering a SWG with High CH

[MinerJason]

I considered installing a SWG during my big pool remodel a couple years ago, but couldn't quite fit it in the budget. I've been using the TFP method to maintain my pool with great success since the remodel, but adding liquid chlorine every other day is a slight hassle for my family when I'm traveling for work, which is often. So, once again considering installing a SWG.

The concern I have is with my current pool chemistry. We have very hard fill water, and high evaporation rates, so my TA and CH are pretty high. I do add acid and then run the sheer descent to keep the TA in check, but the CH slowly gets higher every year. I've never worried too much about scale, and have allowed the CSI to hover in the +0.3 - 0.4 range, which does result in a bot of scale on the waterline tiles, but we don't really mind.

My concern is that trying to keep similar levels with a SWG won't work as well. Am I going to need to drain and refill some water to drop the CH and get my CSI more neutral to run a SWG? If I don't, will I end up cleaning scale off the SWG every couple weeks, reducing the life of the cell? If I do need a more neutral CSI, what CH should I target to make it easier to manage?

Test results from yesterday for reference:
FC - 4.0
pH - 7.5
Ta - 110
CH - 816
CYA - 45
Temp - 82°
CSI - +0.4

 

[PoolGate]

It's funny you guys in the desert are constantly batttling to keep your CH down and I can't get enough I am always adding it.

Perhaps try to get your TA down so that you can get your CSI a little lower.

 

[Rancho Cost-a-Lotta]

If I do need a more neutral CSI, what CH should I target to make it easier to manage?

With high TA and CH fill water, you want to start with a CH of 200-250. I'm assuming that's close to your fill water CH? If so, that means a full drain/refill. You can start higher, but you'll have to replace water sooner.

If you can find a way to top off with softened fill water, very little CH will make it into the pool, so you can start with a higher CH level around 500. Do you have a whole-home softener? If you have water, power and a place to dispose of the effluent, a pool-dedicated automated system would work. A few of us use portable RV softeners. A bit of a pain to flush, but they do help to stabilize CH levels. Check out the link in my sig.

Is that a typo for your CH level? 816 is not a valid result for Taylor-based tests.

 

[an1vrsy]

Do you have a whole house water softene? You could plumb that to hose or your auto-fill to only add virtually zero CH when topping the pool up. If no whole house water softener there are TFPers that use a RV water softener. It would be more effort to regenerate but it would probably be worth your time to investigate.

edit: @Rancho Cost-a-Lotta typed faster than me.

 

[MinerJason]

It's funny you guys in the desert are constantly batttling to keep your CH down and I can't get enough I am always adding it.

Perhaps try to get your TA down so that you can get your CSI a little lower.

Ha! Yeah, it's just a constant struggle to keep the pH and TA low with this much CH. Wondering how much I need to drop the CH to make it more manageable, and how much more it will matter if I'm switching to SWG. Currently is just causes a bit of minor scaling, which I don't care about too much, but if it'll impact the SWG significantly then I may need to manage it more closely.

With high TA and CH fill water, you want to start with a CH of 200-250. I'm assuming that's close to your fill water CH? If so, that means a full drain/refill. You can start higher, but you'll have to replace water sooner.

If you can find a way to top off with softened fill water, very little CH will make it into the pool, so you can start with a higher CH level around 500. Do you have a whole-home softener? If you have water, power and a place to dispose of the effluent, a pool-dedicated automated system would work. A few of us use portable RV softeners. A bit of a pain to flush, but they do help to stabilize CH levels. Check out the link in my sig.

Is that a typo for your CH level? 816 is not a valid result for Taylor-based tests.

That is a typo, should be 825 CH (33 drops). Fill water CH fluctuates seasonally, but yeah, it's generally around 225-250 most of the year. I could time the drain and refill to early fall when the fill water is at the lowest CH levels to help out slightly.

No whole home softener. Have considered it, partially due to the pool water issue. I'll check out the portable RV softener, and see if that makes more sense than a whole house system. I appreciate your input, thanks.

Any sense on how much the CSI matters for SWG? If I don't keep it pretty close to neutral will I encounter problems?

Do you have a whole house water softene? You could plumb that to hose or your auto-fill to only add virtually zero CH when topping the pool up. If no whole house water softener there are TFPers that use a RV water softener. It would be more effort to regenerate but it would probably be worth your time to investigate.

edit: @Rancho Cost-a-Lotta typed faster than me.

Yeah, thanks. Looking into both now.

 

[Rancho Cost-a-Lotta]

Any sense on how much the CSI matters for SWG? If I don't keep it pretty close to neutral will I encounter problems?

In my experience, with a SWG, higher TA and CH levels lead to calcium scaling in the cell (and flakes in the pool), despite maintaining a negative CSI. Check out my thread.

Calcium Flakes in Properly Balanced Pool with SWG

According to @mknauss, "The process of generating chlorine and hydrogen gas creates a high pH environment in the cell itself." When coupled with higher levels of TA and CH and warmer water temps, scale forms in the cell.