Measuring sodium tetraborate (borax)

[waterbear]

HOw are you testing your water otherwise? If you are using strips I would strongly recommend getting a Taylor K-2006 test kit. Also, post a full set of test results. so we can see what is going on in your pool.

New plaster will cause pH rise because the curing process (which can take a year to complete) produced alkaline material in the water. Once the plaster fully cures the pH becomes more stable. If you needed to replaster the pool because of water balance issues then we really should see your current numbers, IF your pH was normally rising before the replaster then your TA was too high. Period. However, with new plaster this is not necessarily the case. Your test resutls (not done with strips please!) will tell us more.

[Rebecca]

I had to replaster because it had been about 20 years! I'm using a HTH 6-way test kit which is basically the Taylor 2006 packaged under the Wal-mart brand name for about half the price.

Speaking of testing, I've been looking all over this morning for those LaMotte borate test strips and can't find them anywhere except in bulk through LaMotte. Where are ya'll getting them?

If I can find them, then I can answer my own question: If you use borax to put TA within the desired range, are you also automatically putting sodium tetraborate within desired ranges?

In the meantime, I'll breathe a little easier in the hope that I probably didn't get sodium tetraborate too high and even if I did, it might not matter.

Thanks,
Rebecca

[Watermom]

Click on the testkit link in Ben's post above. You can get the test strips there.

[BigDave]

... HTH 6-way test kit which is basically the Taylor 2006 packaged ...

I can't agree with you here. The most significant difference is the K-2006 provides FAS-DPD testing for Free Chlorine and Combined Chlorine, the HTH 6-way from wall mart provides OTO testing for Total chlorine. Both tests have a place, but, when shocking a pool or running CYA levels over 50 you need FAS-DPD.

[PoolDoc]

HTH 6-way has OTO testing, which is desirable for daily testing, but (as Dave notes) doesn't replace the FAS-DPD test. Also, the 6-way tests TOTAL hardness, not CALCIUM hardness. (K2006 tests calcium). And the 6-way only has enough reagent for 3 CYA tests, instead of 9 (I think) in the K2006.

[Rebecca]

I'm learning a lot... Thanks for helping me finesse.

1. Okay, I see. Here's the actual product link:
http://www.loveyourhottub.com/lamott...a-test-borate/

2. You can buy a Taylor refill for the cyanuric acid (very cheaply) and use with the HTH kit.

3. I haven't shocked the pool since going to the BBB approach. I try to run CYA at 30-40.

4. Frankly, I assumed that calcium hardness and total hardness were either the same or equivalents, since the HTH kit says the remedy for low hardness is adding calcium. Please continue my education.
Rebecca

[waterbear]

Total hardness is calcium and magnesium hardness. With plaster pools we are only interested in calcium hardness since if the calcium is too low the water can be aggresive to the plaster finish. Totql hardness is really a useless test for pools (strips only measure total hardness also.)
Also, OTO only tests total chlorine. FAS-DPD tests free and combinced chlorine, is not a color matching test but rather a drop counting test similar to the TA and Hardness tests and can directly measure chlorine levels as high as about 50 ppm with a precision of either .5 or .2 ppm.

[Rebecca]

Calcium hardness/Total hardness.

Has anyone actually experienced a situation where they had high hardness but low calcium hardness? I know its theoretically possible but I suspect it's rare. I think the principal contributor to magnesium hardness in water is dolomite. As I understand it, very large concentrations are rare on Planet Earth. In my area, dolomite is associated--in a limited distribution--with lead and zinc mining.

When I filled my pool after resurfacing, total hardness was low. I can't remember the exact number but it was less than 100. It was probably 70 because that's what our lake water tests at. I suspect that hardness is largely calcium based because of limestone formations under the lake and in watersheds. I added calcium carbonate. The water hardness increased to about 220 and has since risen to 300 without any additional calcium carbonate.

Where did the additional hardness come from? As it happens, I harvest rainwater from a roof into the pool. Apparently, ground or pulverized limestone (calcium carbonate or GCC) or dolomite (calcium magnesium carbonate) are used extensively in asphalt shingles. So it looks like I have a situation that may call for calcium hardness testing. Thanks for alerting me to this. Rebecca