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Water testing for spa?


DougA

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Curious what test strips, liquid tests, kits, etc. do you think are a good balance between accuracy and price for.....

clorine

Alk

PH

cya

Calcium

MPS

and anything else I should be testing in my fresh water spa with Nature2 purification with MPS.

 

Thank you, Doug

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If you used strips in addition to the Taylor kit for frequent testing, what test strips do you like the best?  We used our hot tub daily or more.  With the strips you're recommending, are there tests on the strip that are especially inaccurate and you should always use th Taylor kit

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13 hours ago, DougA said:

 With the strips you're recommending, are there tests on the strip that are especially inaccurate and you should always use th Taylor kit

I would not use strips for TA, Hardness (they only test total hardness, which is really a useless parameter. You are interested in calcium hardness), and CYA. Most strips have a pH range that is very wide but the resolution is so large that you really don't know where the pH is. Almost all strips jump from 7.2 to 7.8 and that is way to wide a range for pH. Granted your pH should be in that range but the fact of the matter is that the lower you put the pH the faster it will rise and because of the amount of aeration in a tub, pH rise from outgassing of CO2 is a major problem (correctable in the most partly running a low TA of around 60 ppm or even lower.The TA test also suffers from low resolution. Most test strips have a resolution of 40 ppm and Ta needs to be adjusted to 10 ppm, which a drop based test will do.CYA tests on strips sare affected by pH so they are notoriously inaccurate. This leaves the chlorine tests. They are ok and can be used for a a quick check so don't waste money on 4 way or 5 sway or 6 way test strips. Get a three way strip such as the LaMotte InstaTest 3 way and you will be able to check FC.

However, IMHO, an inexpensive OTO/pH tester with liquid reagents is a better idea for quick checks and almost as fast as a strip. I recommend the Taylor k-1000 because they put a chlorine neutralizer into the pH reagent to help prevent false high readings when chlorine levels are high. They say that the pH results are accurate and precise up to 10 ppm FC and in my personal experience by double checking with a glass electrode pH meter I have found that it's actually a bit higher than that. Most inexpensve (read that as cheap) OTO/pH test kits top out at about 3 ppm FC before giving false high pH readings and some of the expensive ones and ones that use a meter to read the results top out at around 5 ppm. The only downside to using OTO vs DPD, FAS-DPD or syringaldazine (used in some test strips)  for testing is that OTO only tests total chlorine. The upside is that it does not bleach out at shock levels of chlorine like DPD, have a limited range like syringaldazine. Then again, for a daily checks you really want to know if there is chlorine or bromine present and, with bromine you only need to know Total Bromine anyway since bromamines are effective sanitizers, unlike chloramines. Your big test kit should be used weekly or when the strips or 2 way test kit shows that something is out of whack. As a rule of thumb, once you have your water fairly stable, test sanitizer weekly using FAS-DPD (Taylor K02006), it is much easier and does not bleach out like DPD does (Taylor K-2005, all Lamotte test kits, and just about anyone else that uses DPD testing for chlorine/bromine) Test pH weekly and use the acid demand tests to adjust if necessary so you are not guessing how much acid to add (since pH rise is common in spas and acidic trichlor is not normally used you will probably never use a base demand test), Test Total Alkallinity weekly to monthly. IF you are using MPS test weekly since it is acidic and will lower TA faster than dichlor. Bleach is pH neutral (alkaline on addition, acidic on oxidation of organics in the water for a net neutral pH). Test calcium hardness biweeklhy to monthly since it will only drop by splashout. It depends on how often you top off the tub, check CYA the same as calcium unless dichlor is your primary chlorine source.  IF so you might want to consider switching to bleach (which does not add CYA) once the CYA is 30 ppm since high levels of CYA requires higher levels of FC for the same sanitizing effect.

MPS is a different animal. MPS test strips are identical to Combined chlorine test strips so if you have used both chlorine (or bromine)and MPS you will not have an accurate MPS reading IF you use chlorine you will be testing BOTH combined chlorine and MPS and if you are using bromine and have an established bromide bank in the water you will only be testing total bromine since the MPS will react almost instantly with the bromide bank to create hypobromous acid (bromine sanitizer). The ONLY test I know of that will tell you MPS levels without other interference is the add on that Taylor makes for their K-2005 and K-2006 test kits. The K‑2041 (. 75 oz) and K‑2042 (2 oz) are the add ons. Taylor also has a stand alone kit, the K‑1518 FAS-DPD chlorine/monopersulfate test but it is very expensive and really designed for the professional market

Bottom line, my recommendation is a Taylor K-2006 or K-2006C (only difference is that the K-2006C has 2 oz bottles of reagents instead of 3/4 oz bottles) and a Taylor K-1000 OTO/pH test kit for daily checks. If you are using MPS then you also want a Taylor K-2042 with a 2 oz bottle of reagent since it is only about $5 more than the K-2401 with a 3/4 oz bottle. The only downside is if you have a K-2006 and not a K-2006C the bottle will not fit inside the test kit box.

I do not recommend strips (except for a few special purpose ones such as AquaChek or Hach salt titrator strips for salt systems and LaMotte borate test strips if you decide to use borate in your tub (HIGHLY RECOMMENDED for several reasons, least of which is better pH control when used properly). The Lamotte strips are far superior to the Hach, AquaChek, and Taylor borate strips because they are much easier to read). The LaMotte have a color range from rose pink to tan while the other strips are very close shades of tan making the LaMotte strips a clear winner.)

 

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Waterbear....thank you very much for your details above.  VERY helpful.

When you say, " test sanitizer weekly using FAS-DPD (Taylor K02006)," what is the sanitizer???? Do you mean chlorine or bromine or mPs or whatever you use OR do you mean something else?

Thanks, Doug

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