Need help with SWG cost analysis (specifically, salt consumption estimate).

[calinb]

With the increase in LC prices this year, I decided to try to pencil out the costs of running a Jandy Truclear SWG. I lose about 2 ppm FC from my pool per day during the hot summer months. At current Walmart bleach prices (best non-sale LC price locally), that's about $1.50 per day! Last year I diluted 10% pool LC to 5% when it was on sale at the end of the season at Kmart and ACE hardware, filled empty jugs, and stored it in cold (and dark) storage. for this season. (We live on a 1908 homstead and it has wonderful cold storage.) The LC temperature/concentration vs. half life chart I once saw here in the forums was confirmed--the LC lost very little potency while in storage after it was diluted to 5%. The bottom line is end of season sale prices might bring LC prices down to about $1 per day or a little more for me.

I only digress in my LC price analysis to provide an idea of a reasonable cost target in an SWG cost comparison. From SWG posts and other online data, I've estimated my cost for SWG electricity and cell replacement reserve at about fifty cents per day. That's cheaper than even the cheapest trichlor pucks (about $0.66 per day for my usage level)!

I'd like to know how much salt an SWG would use in producing 2 ppm FC in my pool. Then I can add the cost of the salt to my $0.50 / day estimate.

Thanks for any help!

 

[Mr Bruce]

Absent a large water replacement, the salt doesn't go away. The chlorine turns back into salt when it's used up, simply speaking. Plus, just about everything you add to the pool also adds salt. So hypothetically it would actually increase over time with no additions.

 

[ajw22]

Salt is not consumed by SWG use. Salt is lost by water draining, overflow, and splash out.

You have your cost for the initial salt level. So far this year I have needed to add two 40lb bags of salt that cost $7-10 each.

Others who have looked at SWG economics conclude it costs about the same as LC or pucks but is much more convenient.

 

[Mr Bruce]

Plus keep in mind with estimate that your pool probably has a salt level of around 1000ppm. K-1766 will let you know for sure.

 

[mguzzy]

I typically add about 80#s of salt ($15bux or so) at the beginning of the year to account for the dilution from the winter rains. This is the first year in 15 years of swg ownership that I had to add salt again.. due to late season rains I had to drain some of the pool, and that was less than a 40# bag.

Keep in mind.. strictly looking at the cost of Chlorine vs the cost of a SWG in calculating its worth I have found the break even point is around 5 years. But that does not take into account how much easier it becomes to manage the whole pool with one. If I could put a value on the time I've saved It easily paid for itself in the first year.

 

[Divin Dave]

What others said.
The salt doesn't get used up. The sodium hypochlorite turns back into sodium chloride again. On average over a periord of time, depending on how much rain you get during the swimming season, You might expect to have to add 4 to 6 bags a year to replenish what gets depleted by overflow/ splashout.

In winter, if you winterize and drain the water below the returns, then you need to account for a little more salt to wake the pool back up come springtime.

I have a SWG and my opinion whatever its worth, the value of the SWG system is much more than just the cost of it vs luquid chlorine. In my world, there is value to peach of mind, simple convenince and not having to lug around jugs of bleach from the store every few days or so.

 

[calinb]

Thanks so much, everyone! I think there's an SWG in my future. I recently bypassed a nasty underground plumbing leak (~165 gal. / day) to some old leaking and worthless solar panels by replumbing and bypassing the leaking pipes. I left a nice spot on the equipment pad in the pump shed for installing a Truclear SWG using unions.

Plus keep in mind with estimate that your pool probably has a salt level of around 1000ppm. K-1766 will let you know for sure.

I don't know how reliable it might be but I got a cheap TDS meter off Amazon. It says bottled distilled water is 0-1 ppm, our spring fill water is 70 ppm (which agrees well with a local lab report) and the pool is only at 665 ppm TDS. Of course that number includes NaCl and everything else dissoved in the pool water. I'm sure it's currently on the low side, because of my previous water leak and also back flushing the sand filter reduces TDS.