Hot tub filters and chlorine tablets do most of the work of keeping your water clear. Filters trap dirt, oils and debris, while chlorine kills bacteria. Get both right and your water stays fresh for months. This guide explains how each works, how to look after them and the mistakes to avoid.
What do hot tub filters do?
Water is pumped through a pleated cartridge filter many times a day. The pleats catch hair, skin cells, body oils and dust. Over time, those pleats clog up. When that happens, water flow drops, the heater works harder and your sanitiser has to deal with more dirt. As a result, clean filters save you money and chemicals.
How often to clean hot tub filters
- Rinse: every one to two weeks with a garden hose, working between the pleats.
- Deep clean: every one to three months with a filter cleaner soak to remove oils.
- Replace: usually every 12 to 24 months, or sooner if the pleats are damaged.
Tip: keep a spare set. That way you can swap filters while one set dries, which helps them last longer.
How chlorine tablets work
Chlorine tablets slowly dissolve to release chlorine into the water. They are usually used in a floating dispenser. Many hot tub owners in Ireland use small 20g tablets, as they dissolve at a steady rate. However, tablets are only one part of water care. You still need to test the water and adjust pH.
How many chlorine tablets in a hot tub?
There is no single answer, because it depends on the size of the tub, how often it is used and the tablet strength. As a guide, aim for free chlorine of around 3 to 5 ppm. Start with one tablet in the floater, test after a day and adjust the floater vents. Always follow the instructions on the product label, and never put tablets loose on the floor or in the filter housing.
Chlorine tablets vs granules
Granules work fast and suit shocking the water after use. Tablets, on the other hand, give a slow, steady dose between soaks. Many owners use both. If you prefer something gentler on skin, compare chlorine vs bromine first.
Common mistakes to avoid
- Never mix chlorine and bromine products.
- Do not use swimming pool tablets with high stabiliser in a hot tub unless the label says it is safe.
- Store chemicals in a cool, dry place away from children and pets.
- Do not run the tub without a filter, even for a short time.
For safe chemical storage advice, see the Health and Safety Authority. For a full routine, read our hot tub maintenance guide.
Frequently asked questions
How often should I clean my hot tub filter?
Rinse it every one to two weeks, deep clean it every one to three months and replace it every 12 to 24 months.
How many chlorine tablets should I put in my hot tub?
It depends on the tub size and tablet strength. Start with one tablet in a floater, then test and adjust to keep free chlorine at around 3 to 5 ppm.
Can I use pool chlorine tablets in a hot tub?
Only if the label says they are suitable for hot tubs. Some pool tablets are too strong or contain high levels of stabiliser.
Why is my hot tub cloudy even with chlorine?
A dirty filter, unbalanced pH or high bather load are the usual causes. Clean the filter, balance the pH and shock the water.
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