Hot Tub Water Care: The Simple Version

Water care puts more people off buying a hot tub than the price does. That is worth saying upfront, because it should not. The chemistry sounds complicated, the product ranges in the shop look bewildering, and somewhere online someone will have told you it is a part-time job. It is not. Ten minutes a week is realistic, once you know what you are doing.

Graham, who has been commissioning hot tubs in Hampshire for more than twenty years, puts it simply: most water problems come from not testing often enough, not from getting the chemistry wrong. You can fix a water problem in an afternoon. You cannot fix weeks of ignoring it quite as easily.

This guide covers what you actually need, what to do each week, and what to do when the water needs a full reset.

What you actually need

The full range of hot tub chemicals looks intimidating. Most of it you will not touch until something specific goes wrong. For a standard routine, you need four things:

• Test strips (or a liquid test kit if you prefer). These tell you pH, total alkalinity, and sanitiser level in about thirty seconds.
• pH adjusters (pH Up and pH Down). Two small bottles. You will use them to keep the water comfortable and to protect the equipment.
• Sanitiser. This is chlorine or bromine, usually in granule or tablet form. Chlorine is faster-acting and suits hot tubs that get used several times a week. Bromine is gentler on the nose and better for people with sensitive skin. Both work well.
• Non-chlorine shock. A weekly oxidiser that clears out organic waste (sweat, oils, products) without affecting your sanitiser level. Add it after a heavy session or once a week regardless.

That is it for the basics. Some owners also use a water softener if they are in a hard-water area of Hampshire, and an enzyme-based product to reduce scum lines. Both are useful but neither is essential to start.

The weekly routine (about ten minutes)

Pick one regular day and do this every week. Consistency matters more than precision.

1. Dip a test strip. Hold it in the water for about ten seconds, then hold it still (do not shake it) while you read the result against the colour chart. You are checking three things: pH, total alkalinity, and sanitiser level.
2. Adjust pH if needed. Target range is 7.2 to 7.6. Below that, the water becomes acidic and irritates skin. Above 7.8, your sanitiser stops working properly and the water starts to scale the heater. If it is off, add pH Up or pH Down in small doses, run the jets for five minutes, then retest.
3. Top up sanitiser. Add your chlorine or bromine according to the manufacturer’s dose for your tub size. Most 5 to 6 person tubs hold around 1,000 to 1,500 litres. Check your handbook for the exact figure.
4. Add non-chlorine shock. Do this last, with the cover off. Leave the jets running for ten to fifteen minutes before replacing the cover.

A good target: test before you get in, not after. If the water is right, you enjoy the soak knowing it is fine. If it needs adjusting, you have time to do it. Testing after the fact is like checking the weather after you have already got soaked.

The monthly routine

Once a month, do a slightly more thorough check alongside the regular routine.

• Rinse your filter. Remove the cartridge filter and rinse it thoroughly with a hose. Do not use a pressure washer on it as this can damage the pleats. A proper chemical filter cleaner every three months will extend its life significantly.
• Check total alkalinity. This is the buffer that keeps your pH stable. Target is 80 to 120 ppm. If it is consistently drifting, alkalinity is usually why.
• Clean the waterline. A quick wipe around the shell at the waterline removes the thin layer of oils and sunscreen that builds up. A soft cloth and a small amount of surface cleaner does it. Do not use household cleaning products as they foam badly in a hot tub.
• Check the cover. Lift it and look underneath. A cover that has absorbed water adds weight and loses insulation value. If it is noticeably heavy, or if you can see water inside the foam, it may be worth replacing.

When to drain and refill

Every three to four months for most households. Some people stretch to five months if the tub is used lightly and the chemistry stays stable. If it is used heavily, four months is a better target.

The reason is total dissolved solids (TDS). Everything that goes into the water, including chemicals, skin care products, body oils, and the chemicals themselves as they break down, builds up over time. Eventually you reach a point where the water stops responding well to treatment. A fresh start is easier and cheaper than fighting chemistry that is exhausted.

The drain and refill itself takes a couple of hours. You need a submersible pump or a drain valve, a fresh hose fill, and a small amount of line flush product added the day before. Graham’s tip: add a sachet of pipe cleaner the evening before you drain. It pushes any biofilm out of the internal pipework before the water goes.

Common mistakes

These come up regularly when customers call us after a problem.

• Adding chemicals and getting straight in. Sanitiser and shock need time to disperse and off-gas. Wait at least twenty minutes, longer if you added a large dose. Run the jets with the cover off.
• Guessing instead of testing. The water can look perfectly clear and still be badly out of range. Test strips are cheap. Use them before every session if you are in any doubt.
• Ignoring pH for weeks. Low pH corrodes seals and the heater element over time. High pH causes scale and reduces the effectiveness of your sanitiser. Both are slow-burn problems that become expensive if left long enough.
• Overdosing chemicals to fix a problem fast. More is not quicker. A large dose of sanitiser will raise chlorine to a level you cannot use the tub until it drops back down. Small, measured doses with a retest in between are always the right approach.
• Showering before you get in. Yes, this is worth doing. A quick rinse removes body oils and products that would otherwise go straight into the water and consume your sanitiser.

What we do for you

When we install a tub, we commission it and fill it ourselves. We test the water, balance the chemistry, and walk you through the routine in person before we leave. You do not start from a standing start.

We also put together a starter chemical kit for every new installation, with the products we would use ourselves and written instructions in plain English. Mark has put together a one-page quick-reference sheet that covers the weekly and monthly routine. It lives on the side of most people’s filter compartment.

If the water ever goes wrong after that, call us. Nine times out of ten we can talk you through it on the phone in five minutes. If it needs a visit, we will arrange one.

Water care is not complicated once you have done it a few times. The first three months are the learning curve. After that it is just a habit, like checking the car tyres.

If you have questions before you buy, come into the showroom or call us. We are happy to go through the routine with you before you commit to anything.