Am I reading the test results correctly?

Muskotten said:

Hey there fellas!

I recently bought a house with a indoor swimming pool. I'm completely new at this.
I started reading up and then I ran some tests (pH, FC, TA, CYA, Br) and got the results:
pH: 7.8
FC: <0.1
Br: <0.2
TA: 175
CYA: >200

Since the CYA levels were sky high I drained and replaced the water in the pool until I got the CYA levels down.
Vaccumed and scrubbed several times.
Then I added some flocc.
I shocked the pool with HTH Chlorine granulate (which is 65% calcium hypochlorite).
Now it's been 4 days since I shocked and I've got the new test results here.

Now to my questions, I just want to make sure Im reading the tests correctly before I jump in so, could anyone please take a look at the results and tell me if:

1. I'm reading it right?
2. If I'm doing the TA test properly? I don't know if I should stop adding water to it as soon as it turned from red to the murky brown/purple or til its dark turquoise or if I should keep going til its actually bright green?

This is what I think the test results tells me:
pH: 7.6
FC: 1.8
Br: 3.0
TA: 160
CYA: ~10
(I don't have a picture of the CYA test but I'm sure I've got that one right)
The pool temperature is 90°F if it matters.
Here is pictures of the test results:
View attachment 557234
View attachment 557235View attachment 557242

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Welcome! The pH is probably close enough but we don’t trust those color comparison pool tests and you can see why. What’s the dark block colored test?

I can help a little bit in that you don’t have Bromine in the pool then you don’t need to test for Br. They just share the same scale. Do you have a way to get a Taylor test kit?

Muskotten said:

If I'm doing the TA test properly? I don't know if I should stop adding water to it as soon as it turned from red to the murky brown/purple or til its dark turquoise or if I should keep going til its actually bright green?

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I tried to look up this Lovibond 4 in 1 test set but found lots of images but no clear understanding how it does its test. There is even a reference to photometer 4 in 1 test set. not sure if you have that.
The TA test using the Taylor Technologies test kit (K-2006) is the reagent (R-0008) turns the water sample green then as you add drops of reagent (R-0009) the water sample will turn first to purple then continuing with drops will finish when it cherry red. It does not appear you are using these types of reagents so not sure if we can be helpful until we understand how your test kit works.

I don't think there will be many around here that know this specific test. It seems to work in the opposite direction to the Taylor test.

The Taylor test works by adding an indicator that changes from green (above pH 4.5) to red (below pH 4.5). Buffered water has Alkalinity zero at pH 4.5. By adding and counting drops of acid until the indicator changes to red (i.e. when reaching pH 4.5) you can measure to Total Alkalinity of the sample.

Your test seems to be based on the same indicator system but contains acid in the tablet. By first dissolving the tablet in a small sample volume the acid contained in the tablet is enough to pull the sample's pH below 4.5. Then you add more and more sample water until the acid can no longer pull pH below 4.5. The amount of water is then a measure for the Total Alkalinity in the sample.

When we do the Taylor test the other way round, we add acid drops until the sample is fully red and the shade of red doesn't change when adding more drops.

Assuming that the used indicator is the same, I'd say that you would have added too much water once it is green. You want to find the point just before the red starts changing. That's not easy as you keep diluting the sample more and more as the test proceeds, changing the colour intensity. An interesting test idea, but I'd prefer a test like Taylor where the sample volume is fixed and you don't meddle with the indicator intensity.

But all of that is a bit of guesswork, maybe @JamesW or @JoyfulNoise have experience with this type of test.

If there is any chance to order a Taylor test, then do it, it's worth every penny. It works, folks around here know it works and they will be confident to give you advice based on your test results, without fearing to ask you to do something that could actually damage your pool (like reducing your TA because of a wrong interpretation of your test).

There are a couple of members from Europe round here. In the end they often converge towards ordering a Taylor kit after all (it should be the K-2006 or K-2006C that comes with larger reagent bottles).

One source is this one:


And welcome to TFP

Muskotten said:

Alright chief, Br test is in the bin.
But if you were to try reading the Cl levels in my test what would your guess be?
The test in the cylinder shaped container is for TA.
I tried to find a Taylor test first but it seemed a bit hard to get on the eu market and expensive. It was like navigating in a jungle with all the different preferences and opinions people had so I just tried to find something that was better than the useless pH strips I had inherited from previous owner

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My guess would be 1.5 but that’s all it would be. Best I could say was more than zero and less than 5. If you really do only have 10ppm CYA. That would be the first thing I’d increase to 30ppm and then get your chlorine up to 5-7ppm so it follows this chart.

I know it may be hard to get the accurate test kit but that would be a priority if at all possible.

Muskotten said:

This is the test I'm using: 4 in 1 testset DPD, pH, totale alkaliteit en cyanuurzuur | Zwemland.nl
I actually found these pictures on lovibond.com now. I only had the intructions text before, wish they had included the pictures or at least a colour sample too, that would've been very helpful
So maybe I should add some more water to the test since mine looks a wee bit darker than their description.
View attachment 557357

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@mgtfp provided a very good explanation on the relationship between the Taylor test kit and your Lovibond 4 in 1 test kit.
The only thing I could add would be to use a dropper to add a drop of pool sample at a time (rather than pour the pool sample). This would avoid overshooting the mark and also be very similar to how the Taylor kit works in that drops are added at the point of color change and you stop when no more color change.
This test kit is probably workable once you get the hang of it. How do you test CH? However, I must say that the Taylor kit used the FAS/DPD test for chlorine is much better than color matching

Muskotten said:

Only thing is that it's in spanish and my spanish is non-existant, even though I think I can guess what 'cloro' means

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Just turn on the automatic translation that chrome offers in the browser menu in the top right corner (not the web page menu), it's surprisingly good these days:

Muskotten said:

My pool is indoors so the sun wont break down the chlorine. As I understood it I shouldn't need CYA in my pool if It's indoors? Please correct me if I'm wrong

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TFP recommends to add a little CYA (about 20-30ppm) to indoor pools as a chlorine strength moderator:


CYA changes the chemical equilibriums. Without CYA there is only a pH dependent equilibrium between hypochlorous acid (HOCl) and hypochlorite ion (OCl^-). At low ph, it's mostly HOCl, at high pH mostly OCl^-. HOCl is the one that has excellent sanitising and oxidising properties, that's why the pool industry recommends to maintain pH below 7.5.

With CYA, most of the chlorine (Let's say 95-97%) forms a chemical bond with CYA as chlorinated cyanurates. In this bond, chlorine is protected from UV light, but doesn't have any disinfecting properties. Unfortunately, it still shows up as FC in the tests, and that's where the confusion starts.

Regulators in Europe (I know that Germany is doing it that way, not sure about the Netherlands) react to this by just banning CYA outright in public pools. But at the same time they acknowledge that in this case FC should be kept below 0.6pmm (and above 0.3ppm).

In the US, the effect of CYA is largely being ignored. At low levels, it's UV protection is appreciated, but the effect on the chlorine efficiency is not understood and ignored, until at CYA 100 a mysterious "chlorine lock" occurs.

TFP follows the way of actually tackling this at the root. After Ben Powell found experimental evidence that FC needs to be adjusted to the CYA level, Richard Falk (aka chem geek on the forum here) looked up the relevant scientific publications (it all goes back to an O'Brien paper from 1972), and provided an explanation for Ben's observations. Details are all in chem geek's sticky threads in the Deep End forum.

In a nut shell: To maintain same HOCl concentrations, the FC/CYA ratio must be kept constant. That's it, the results are summarised here in the recommended FC/CYA Levels.

The level of FC 0.6ppmm that is considered the upper limit in Germany is roughly equivalent to TFP's SLAM-level (for example FC 20 at CYA 50 or FC 16 at CYA 40 - same FC/CYA ratio). Everything below SLAM is considered safe for swimming. And everything below the minimum level is will result very quickly in an algae outbreak and is borderline unsanitary. Therefore maintain FC within the recommended target ranges.

The big advantage that maintaining FC in the target range (lets say FC 6-8ppm for CYA 50ppm) offers vs maintaining FC in the appropriate range between 0.3 and 0.6ppm without CYA is, that the latter is bloody impossible in a residential setup without fancy, expensive testing and dosing equipment. Let's say you have a couple of kids swimming that are too excited to go the the bathroom, and you will have lost all your 0.6ppm very quickly - urine eats up chlorine in no-time. Or a very sunny day with an outdoor pool. When losing 0.6ppm from a level of 6ppm, you are still within your target range, and miles ahead of your minimum level. The chlorinated cyanurates are basically providing a chlorine reservoir. Chlorine in the reservoir is protected from UV and basically not reacting with anything. In other words, it doesn't feel "harsh".

And this is the effect, that an indoor pool will also benefit from. You don't need it for UV protection, but a small level will allow you to keep FC within an easy to maintain target range, or in an even bigger range up to SLAM-FC - remember that SLAM is equivalent to about 0.6ppm without CYA which is considered the upper swimmable level under German regulations for public pools.

CYA also adds the benefit that it flattens the pH-dependency of the HOCl concentration. Without CYA, from pH 7.5 to pH 8.0, the HOCl concentration decreases by about 50% by turning into OCl^-. With CYA, it only decreases by about 15% (as HOCl turns into OCl^- with rising pH, more chlorine gets released from the reservoir, compensating for most of the loss. Therefore, with CYA,, at the appropriate FC/CYA Levels, pH can be maintained anywhere that has a "7" in front of the decimal point. Much easier, with the added benefit that pH will stop rising so fast when allowed to settle a bit higher in combination with lower TA-levels.

The "high" levels of TA 100-120 recommended by the industry are only required when using Trichlor for chlorination as that keeps pulling down pH and TA. Using liquid chlorine or a Salt Water Chlorine Generator is pH- and TA-neutral, and lower TA-levels are possible, and even beneficial as it slows down the constant pH-rise due to CO₂ outgassing (high TA means more CO₂ dissolved in the water that wants to escape like in an opened bottle of soda water).

I hope I haven't overwhelmed you with my short story of nearly everything you need to know about pool care. Have a read through the Pool School articles, browse through the forums and fire away with your questions.