Leave hot water bubbling away in a tub for any length of time without treatment and it soon goes scummy. Before long it’s a sludgy grey soup so horrid you wouldn’t make your worst enemy sit in it. You need the right chemicals, in exactly the right amounts and proportions, plus regular common sense testing. Here’s our guide to hot tub water testing.
How to test the water in your hot tub
First of all, have a look. Basically, if it looks scuzzy, it is probably scuzzy! Other than that you’ll want to know the chemicals are balanced properly, so try these.
Should I go digital?
A digital hot tub water tester is something they use for swimming pools, able to test various things and obviously more expensive. The good thing is you can leave it in the water for instant real-time checking to see if things are getting nasty. They’re also fun when you’re simply a person who likes gadgets. Why the heck not.
Strips or liquid test kits?
They both do the same job, although some say strips are more accurate and they’re definitely easier to use. Just dip it and see. Follow the instructions on the packet, use water from the middle of the spa or hot tub for accuracy, and don’t leave the jets on. You need calm water for the best results, not a tsunami.
Liquid testing requires a test kit including two crucial chemicals: phenol red to test the PH and orthotolidine, also called OTO, to test the chlorine. There’ll be a test tube or container in the kit, to use to collect a small sample for the middle of the tub. Add the right number of drops of phenol red to the pH side, then do the exact same thing for the OTO. Once the required time has passed, dangle the container against a pale background so you can easily see the results against the chart.
Strips offer different pads depending on what results you need. Either collect water in a plastic container from the tub centre or dip the strip directly in. Then wait for the right amount of time and match the results against the chart on the packaging. Testing strips are one of the most simple, effective and inexpensive ways to do it. Some strips do everything at once, testing total hardness, total alkalinity and chlorine, others do specific tests. The instructions for them are different, and they also differ by brand, so never assume you’ll be doing the same thing when you buy different strips to your usuals. It’s wise to wear gloves when testing too, to keep your skin safe.
Chlorine itself
Chlorine stops bacteria, microorganisms and other germs from growing. The total chlorine number shouldn’t fall above or below 1.5 – 3 parts per million. The ‘free chlorine’ measurement, basically the chlorine left in the water after it has done its work killing germs, should read 1 -3 ppm and needs to be higher than your total chlorine reading. And the cyanuric acid in chlorine stabilisers stops chlorine disintegrating in sunlight, ideally 30 – 50 ppm.
Hot tub strips to measure total alkalinity
Strips are seriously handy because they offer a multi-function approach. Your ‘total alkalinity’ is very important, the thing that prevents the PH level constantly changing. The strip measures how much dissolved alkaline is in the water, which should fall between 80-120 parts per million. Unless it is, you’ll never have good water quality and PH maintenance will always be a nightmare.
Balanced pH
A balanced pH level is also vital for good hot tub waters quality. Aim for a perfect 7.2 – 7.8 score and you’re doing great. If it’s lower, maybe because rainwater has got into the tub and messed with your chlorine tablets, the water is too acidic and might irritate your skin and eyes, as well as not doing a very good job of keeping things sanitary. Higher pHs mean it’s too alkaline, just as bad because it doesn’t just irritate the skin and eyes, it also causes scale to build up and makes the water grey. If you’ve left detergent in the water, say from makeup and sun protection creams, it might explain why the pH is too high.
Too much or too little calcium
Calcium is another thing to test for, the calcium in hard water that causes a chalky build-up very like the stalactites and stalagmites found in limestone caves. Use a water softener when filling the tub, or buy a hot tub with a built-in hard water treatment system and save yourself a load of faffing around. When the calcium level is too low, the water and hard surfaces feel horribly slimy, in which case you need a calcium booster.
Bromine is a chlorine alternative, and you need either dedicated testing strips or an all-in-one testing kit including bromine tests. It should fall between 3-5 ppm. Then there’s something called Total Dissolved Solids, basically all the waste that falls off your skin and body, gets into the water from outside, and blows in. Too much of it and you’ll need to change the water for fresh or the whole chemical balance will go wrong, leaving you with the foamy, grey toxic soup you really want to avoid.
Regular water testing matters because it keeps a hot tub safe and hygienic. Keeping it clean means there’s less chance of things going wrong. Chemical imbalances can leave you with damaged pipes and components, skin irritations and even dangerous nasties like Legionnaires disease, mild in most people but fatal for some.
How often do I need to test the water in a hot tub?
Regularly testing the water isn’t difficulty, but it does need to happen to a regular timetable. It’s simple enough once you get into the swing of it, something you need to do once a week to keep thing going nicely and head problems off at the pass before the chemicals in your tub become seriously imbalanced.
How often do I need to change the water in a hot tub?
It doesn’t matter how clean you are, tiny bits of you will always fall off into the water! Once it gets over-saturated with these dissolved substances called – disgustingly – total dissolved solids or TDS, the sanitiser you’re using will stop working, simply because it can’t dissolve in the murky brew. Most hot tub pros ay it’s good to change the water completely every 3-4 months, say once a quarter unless you’ve emptied it out for the winter, in which case you’re looking at 2-3 times a year.
Keep thing sparkling clean and fresh and your hot tub will be a constant pleasure to use.
