Have Salt Systems fallen out of favor?

[dbhutch]

All three of the PBs we received quotes from said that the salt eventually attacks/degrades the natural stone and/or leaves white deposits where it evaporates. One mentioned corrosion to pool equipment. But it was such an instant negative response when I asked about a salt pool installation...that I felt they weren't being upfront with me....that something else was making them recommend against a salt pool. We now have an IG, 15k gallon freshwater pool with flagstone coping and moss rock waterfall. This is our first pool experience....we were interested in getting a salt pool for all of the positives they offer and none of the negatives of a freshwater pool...but the pool builders convinced us to rethink our options. We also talked with six customer referrals and the verdict was 50-50 on salt pools.

[PoolDoc]

Using flagstone coping, as standard, sounds like a local pattern. I'm pretty sure it's not an national one. But, *I'm* not sure I'd want to use salt on a pool with high evaporation surfaces, like waterfalls.

Regarding the positives you think salt has, I'd urge caution. They are commonly oversold as "eliminating pool chemicals", "chlorine free", "natural" and so forth. These are ALL bogus claims.

[drband]

Read somewhere in this forum that the cost savings of a saltwater pool are negligible after you figure in the cost of the system. You can buy a LOT of bleach, borax, and baking soda for the thousand or so that the SWCG will cost. You will still have to balance the pool chemistry the same way, just not use as much bleach as otherwise. If you want the "feel" of salt water, go ahead and add salt to your pool (I have done so and really like the way the water looks and "feels" though this is bound to be somewhat subjective! My salt level is about 2300 ppm as measured by test strips. SWCG's usually need a higher concentration of salt, but 2300 is plenty high enough for the feel benefits.)

[PoolDoc]

I've said that SWCG's are roughly speaking, a financial wash. But I'd been thinking about that more specifically over the last few days. I installed (4) Pentair IC60 units on a 200,000 customer pool this spring, and have been trying to decide if I should add a fifth unit. Here are the numbers I've been considering:

IC60 Chlorine cost:

Cell costs
IC60 cell life: 10,000 hours, or 416 days => 'ON' time
IC60 'daily' or 24hr chlorine nominal production: 2 lbs chlorine gas equivalent.
IC60 likely actual production, over cell life: 70%
IC60 cell cost: ~$1,000
Cell life total production: 416 * 2 * 0.70 = 583 lbs of Cl2 equiv
Cost per pound (considering ONLY the IC60 cell!): 1000/583 = $1.72/lb

Electrical costs
Now, for my purposes, the electricity doesn't cost anything, because the customer does not (and does not want to) pay attention to it. BUT, here it is, anyhow:
Approximate 120V input: 2A or 120 * 2 = 240W
KWH/day = 240 x 24 / 1000 = ~8KWH
$ per KWH in Chattanooga = ~$0.10
$ for electricity over life of cell: 416 * 0.10 = $41.60
Cost per pound (for electricity) = 41.60/583 = $0.07/lb

Salt costs
But, there's another factor -- the salt. So far, I've put 3 pallets of salt into the pool, at a cost of about $1500. It's running low, and I'm going to have to have another pallet. This atypically high use, because this pool leaks about 1" per day. But, I'm going to spend $2,000 on salt for the season. With this pool, my salt will probably last 2 years between draining for various service issues, giving me an average cost of $1000 per year.

Total SWCG produced chlorine cost:
So, the cost per lb of Cl2 for salt -- higher than for most pools -- will be $1000 / $583 or $1.72 (again!)

So my TOTAL cost per pound of chlorine from the IC60's is $1.72 for the cell + $0.07 for the electricity + $1.72 for the salt, or $3.51/lb


Dichlor costs
Dichlor -- 50# at Sams for $106 + $9 tx = ~$115
$'s / lb dichlor = $2.30
lbs Cl2 per lb of dichlor (62%) = 0.62
$'s per lb Cl2 equiv = 2.3/0.62 = $3.71

On this particular pool, chlorine consumption runs about 70 lbs Cl2 equiv / week. So, I'm getting 56# x 90% (my estimate of current actual output) or 50# from the IC60's, and making up the balance with dichlor. But, because of my rapid water loss, I need to make up CYA, which the dichlor provides.

But, my overall cost per # of Cl2 is about $3.75 from either dichlor or the SWCG's.

Now, on a residential pool, costs for the CELL would typically be higher, because the cell cost per pound of SWCG is LOWER for an IC60 than for an IC20. But the water loss would be less (hopefully) and the salt cost would be less because of the volume profile -- this pool has a 4' deep shallow end, and a 13' deep deep end.

The result for my customer? They aren't saving anything.

However, the chlorine level is MUCH more stable, now that I don't have depend on a pool manager who is a great schmoozer (necessary at a country club pool) and on lifeguards who are flaky slackers, but un-fire-able because they are members.

So, costs are the same, but water quality is better.

By the way, just for comparison: *fresh* industrial 15% bleach contains about 1 1/4 lb of chlorine gas equivalent and costs $1 - $2 per gallon. That translates into a chlorine cost of $0.80 - $1.60 per lbs -- MUCH cheaper. However, handling bleach in large quantities is expensive and difficult. So, as usual there's no free ride.

My guess is that costs for CELLS will come down rapidly over the next 5 years, once Chinese units (like Intex's sucky one!) begin to be widely available AND improve in quality. I don't know, but I'd bet SWCG manufacturing is currently a high margin activity.

[waterbear]

All three of the PBs we received quotes from said that the salt eventually attacks/degrades the natural stone and/or leaves white deposits where it evaporates. One mentioned corrosion to pool equipment. But it was such an instant negative response when I asked about a salt pool installation...that I felt they weren't being upfront with me....that something else was making them recommend against a salt pool. We now have an IG, 15k gallon freshwater pool with flagstone coping and moss rock waterfall. This is our first pool experience....we were interested in getting a salt pool for all of the positives they offer and none of the negatives of a freshwater pool...but the pool builders convinced us to rethink our options. We also talked with six customer referrals and the verdict was 50-50 on salt pools.

The use of local natural rock is the reason they recommend against salt. Not all natural rock is created equal. Personally, I would worry about limestone used in any pool since it is a porous rock that is easily eroded and it is by no means chemically inert! IT will have impacts on your water chemistry and can be attacked by more than just salt. Realize that the use of local natural rock is not the only method of pool construction but is often used for cost considerations.

[chem geek]

In addition to the cracking and deterioration of porous stone that is made worse by salt splash-out and evaporation leading to recrystallization pressure, there is also the increased metal corrosion rate from the higher conductivity of the water (around 3x or so) due to the higher salt levels and from stainless steel corrosion from chloride attack from its higher level. However, all of these types of problems can be mitigated through use of proper materials or procedures. Porous stone can be sealed or less porous stone used. More corrosion-resistant stainless steel can be used that contains more chromium or a sacrificial anode can be attached to the bonding wire and buried in moist soil.

In some cases, one does not have a choice because a material such as aluminum will be used in header bars and rails for automatic pool covers, for example. For "vanishing" electric safety covers where the aluminum header bar is immersed in the water, a zinc or magnesium sacrificial anode is recommended.

[PoolDoc]

Maybe we can come up with a list of possible problem components?

I've mentioned heaters and aluminum ladders anchors before, but would have never thought about the auto covers.

[chem geek]

Stone Degradation (soft stone)
----------------------------------
Splash-out and evaporation in areas without a lot of summer rains. So stone coping, mostly.
Possibly outer areas of waterfalls (where water splashes and evaporates).
In particular (as waterbear pointed out), limestone is the worst, though flagstone and really most stones have a variety of hardness so this varies by quarry (so, location).

Metal Corrosion
-----------------
Aluminum top rails for auto-covers
Aluminum header bars immersed for "vanishing" auto-covers
Aluminum or steel filters (rare these days as they are mostly plastic now)
Diving board base (and screws/bolts) from dripped water
Furniture (mostly screws) from dripped water
Inferior stainless steel or zinc-coated materials (such as screws in Intex pools)
Screws, rails, pool cleaner parts (some are metal, such as threaded gears powering the wheels)
Copper heat exchangers (cupro-nickel and titanium are more resistant)
Galvanic corrosion at bonding wire where dissimilar metals meet (occurs anyway, but might be accelerated by positive voltage on bonding wire)

Not all of the above are equal in susceptibility. Problems with heaters, for example, are more rare.

Also note that metal corrosion is significantly exacerbated if there are stray voltages which can occur in some areas. The higher conductivity of the water just makes an existing problem occur more quickly.

[PoolDoc]

Thanks, Richard.

[chem geek]

I forgot light rings that should be added to the list (really wish I could edit older posts!).