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Author Topic: Combined Chlorine, MPS & Jets & Saturation Index  (Read 2602 times)

hailypup20

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Combined Chlorine, MPS & Jets & Saturation Index
« on: March 06, 2011, 04:07:18 pm »
Ok, 3 questions, all hinted upon in the title:

1)  I have the Taylor test kit, and after testing for  Free Chlorine, you have the option to test for Combined Chlorine.  Is there any reason whatsoever I should be doing this test for my spa?  The Combined Cl always comes in at a very low value (0.2-0.5 max!)

2)  I am currently shocking the spa every so often (every 1-2 weeks) with MPS.  Should I be putting on the jets after putting the granules in the water?  If so, for how long?  All jets to get it through the system or just to agitate/mix?  (Please note that I currently turn on the jets for about 3 minutes after adding the MPS to distribute it properly, but want to know if I'm doing it properly)

3)  In my Taylor test kit, there is a little chart (dial) that gives you the Saturation Index.  For those of you with experience, is this a trustworthy source for ensuring things are in balance.  Again, for reference, mine usually is very close to 0 (within 0.2) due to slightly acidic water with a higher-than-desired Calcium Hardness.

Thank you for reading and your time!

Regards - hailypup20

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Combined Chlorine, MPS & Jets & Saturation Index
« on: March 06, 2011, 04:07:18 pm »

chem geek

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Re: Combined Chlorine, MPS & Jets & Saturation Index
« Reply #1 on: March 06, 2011, 07:36:57 pm »
If you are maintaining a proper active chlorine level in your spa and using sufficient oxidizer to handle your bather load, then you should not normally see any significant Combined Chlorine (CC) except perhaps in the hour or so immediately after a soak.  For an accurate CC reading since it is normally so low, you need a FAS-DPD chlorine test such as in the Taylor K-2006 test kit.  So if you are properly maintaining your spa, then you probably don't need to regularly check for CC -- just make sure that FC never gets to zero.

The regular circulation pump is usually sufficient to ensure thorough mixing.  Putting on the jets will aerate the water and tend to make the pH rise faster.

The Taylor watergram is accurate, though you can also use The Pool Calculator to calculate the saturation index and to calculate dosages (after changing for the spa water volume, of course).  Note that 1 ounce is 2 tablespoons or 6 teaspoons.

For an acrylic spa, you do not need to have the water saturated with calcium carbonate since there are no plaster surfaces or grout surfaces between tile to protect.  To reduce foaming, the Calcium Hardness (CH) can be at 120-150 ppm.  It sounds like you have high CH fill water since it's on the high side (unless you added to much CH increaser).

A rough rule-of-thumb for how much oxidizer is needed to handle bather waste in a hot (104ºF) spa with no ozonator is that every person-hour of soaking needs about 3-1/2 teaspoons of Dichlor or 5 fluid ounces of 6% bleach or 7 teaspoons of non-chlorine shock (43% MPS).  If you have an ozonator and use the spa every day or two, then these amounts may be cut roughly in half.  However, the real test is to check the FC level before a soak and ensure there is always some measurable amount (at least 1-2 ppm) and then add enough chlorine after the soak so that you measure FC before your next soak.

If you are using Dichlor-only, then over time the Cyanuric Acid (CYA) level will build up since for every 10 ppm FC added by Dichor, it also increases CYA by 9 ppm.  This will make the chlorine less effective over time so you will need to either shock the water with higher chlorine levels after a month or so or you'll need to use MPS to supplement oxidation.  If you instead use the Dichlor-then-bleach method, then you may never need to shock nor use MPS, but the use of hypochorite sources of chlorine (such as bleach) requires the Total Alkalinity (TA) to be much lower (around 50 ppm) and the use of 50 ppm Borates (such as from Proteam Gentle Spa or boric acid purchased directly) is recommended.

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Re: Combined Chlorine, MPS & Jets & Saturation Index
« Reply #1 on: March 06, 2011, 07:36:57 pm »

 

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