Great Langelier Online Calculator for Balanced Water

[smallpooldad]

The following site from the American Water Works Association and Rothberg, Tamburini & Winsor, Inc. have what appears to be a very good Langelier Index calculator.

http://www.awwa.org/Science/sun/docs/RTWCorrosivityCalc.cfm

From having visited other sites I understand the Ryznar Index is not that important in pools but has been pushed by some questionable sales people for their own benefit. The ideal index here is supposed to be 6.8. I personally have no deep knowledge of the Ryznar Index so I am unable to answer questions, but once again I stress it is not that important unless you have a stainless steel pool. Yes they exist, there is one not far from my house in Honolulu - rust capital of the world after the Red Sea.

Pool temperature and calcium content have a fair impact on the numbers. I believe that it is good to keep the Langelier index within + or -.30, with the PH ideally located at 7.5 (or 7.4 if you are trying to keep iron out as I have to), or at least between 7.4 and 7.6, and alkalinity in plaster pools near 100 and near 120 in vinyl, but I am sure that some would disagree with this statement.

There are as they say "Many ways to skin a bathing suit."

[PoolDoc]

Just another reminder . . . the Langlier Index is popular among pool dealers because it sells chemicals, and not because it's especially applicable to pools!

It does matter *INSIDE* pool heater heat exchangers, but you MUST use the temperature INSIDE the tube (pool temp + 15 - 20 deg) and NOT the pool temperature.

It's also a rough guide to avoiding corrosion in plaster pools, and for allowing you to anticipate calcium carbonate precipitation in pools near theoretical saturation.

But, as Dr. Langlier himself noted, it doesn't really apply to bodies of water exposed to the air; only to closed systems like hot water heating systems.

What's more the whole issue of corrosion of plaster surfaces is far, far more complex than people realize. Sulfates, from things like sodium bisulfate or "dry acid", can be a big player. Aeration, from fountains or waterfalls, can have a huge impact. Plaster pools chlorinated with trichlor frequently show corrosion. There's even some preliminary evidence that high levels of CYA (> 150 ppm) can accelerate plaster corrosion.

What's reasonable is to keep a reasonable pH (7.2 - 7.8), a low to moderate alkalinity (80 - 140) and some calcium ( > 100 ppm on plaster pools ). There's very little evidence that pools maintained in such a way will experience plaster corrosion . . . ESPECIALLY if they are chlorinated with bleach or calcium hypochlorite.

Ben
"PoolDoc"

[smallpooldad]

Thank you for the reply.

Once again I learnt something new from this great forum. And yes I do have a pool heater as the Tradewinds blow and keep the temperature down.

My plaster pool levels ranges are as follows (depending on my follow up):

CYA 35 (I may have to increase this to keep the liquid chlorine demand down)
CL 5 (3-6) Liquid bleach
Calcium 260 (rising very slowly)
Alk 100 (80-110)
PH 7.3 (7.2-7.5)
TDS 560 (naturally increasing slowly)
Temp 22.5 to 24.5 C (weather dependant)

No algae, but continuing an ongoing fight with with airborne rust (ferric oxide). So per Mbar's recommendation I try to keep the PH below 7.4 with a little metal out, seems to be working well.

A quick question, I use to keep my Calcium at 200 but recently raised it to 260, this for some unknown reason seems to keep the iron from coming back into the pool. Is there a reason for this or do you think some other factor is helping?

I think these levels are ok, please advise if not.