How to Keep a Hot Tub Clean (Without Living Inside a Chemistry Kit)

Keeping a hot tub clean is not complicated, but the spa-store industry has spent decades making it sound like a chemistry degree. In reality, four habits and about ten minutes a week keep any tub crystal clear.

Here's the simplest possible routine that actually works — everything else is optional.

The four habits

1. Sanitizer above 1 ppm at all times. This is the whole game. If sanitizer drops to zero for more than a day or two, biofilm starts growing in the plumbing and no amount of shock will fully undo it. Test twice a week and top up.

2. Rinse the filter every 1–2 weeks. Pull it, hose it from the top down at an angle, reinstall. This alone stops 80% of "cloudy water" complaints.

3. Shock after heavy use. Non-chlorine shock (MPS) at the label rate after any soak with 3+ people or anyone who used a lot of body product. Wait 20 minutes before covering.

4. Drain and purge every 3 months. Non-negotiable. See below.

Chemistry basics (memorize these)

• pH: 7.2 – 7.8
• Alkalinity: 80 – 120 ppm
• Sanitizer: chlorine 1–3 ppm or bromine 3–5 ppm
• Calcium: 150 – 250 ppm

Buy a bottle of pH Up, pH Down, dichlor granules (or bromine tabs), alkalinity increaser, and calcium hardness increaser. That's your entire chemistry shelf. Everything else the spa store tries to sell you is optional.

The chlorine vs bromine debate — real answer

Chlorine (dichlor): cheaper, dosed manually, needs testing more often, better at burning off contaminants fast, slight smell at high doses.

Bromine: stable at higher temps, more forgiving of missed doses, uses a floating tab feeder, no chlorine smell, slightly higher ongoing cost.

For a residential tub used a few times a week, bromine is easier because the tab feeder does most of the work between weekly tests. Chlorine wins if you'd rather pay less and test more often.

Drain and purge (every 3 months, 2 hours + refill time)

This is the single habit that separates people whose tubs stay clean from people who fight cloudy water forever.

1. Purge the plumbing first. With the tub still full, add a biofilm remover (Ahh-Some, Oh Yuk, Spa Purge — all similar). Run jets on high for 20 minutes with the air off. You'll see brown gunk pull out of the internal plumbing. That's biofilm — the stuff sanitizer can't reach.
2. Drain fully. Attach a hose to the drain valve or use a small sump pump.
3. Wipe the shell. Non-abrasive cleaner, microfiber cloth. Focus on the waterline.
4. Clean or replace the filter.
5. Refill through the filter housing to prevent airlock — put the hose down into the standpipe where the filter sits, not into the shell.
6. Rebalance in this order: alkalinity → pH → sanitizer → calcium.

Skipping the purge and just draining is a waste. The biofilm stays and immediately re-inoculates the fresh water.

The five mistakes that kill water clarity

1. Adding shock or sanitizer before testing. Overshooting sanitizer bleaches out test strips and stalls all further dosing decisions.
2. Dosing pH before alkalinity. Alkalinity holds pH steady. Fix alkalinity first or pH will bounce forever.
3. Reusing an old filter after a purge. All the biofilm you just released is now trapped in the pleats. Replace or deep-clean.
4. Running the pump only on low all the time. Filtration cycles need to run on high for at least an hour a day for the filter to actually do its job.
5. Letting the cover collect a puddle. Standing water on the cover attracts bugs, sags the foam, and drips contaminated water into the tub when you open it. Squeegee it off.

Why sanitizer sometimes just disappears

If you dose sanitizer and it's gone in an hour, one of three things is happening:

• Chlorine demand — a big organic load (lots of bathers, lotion, sweat) is burning it off. Shock heavier.
• Biofilm in the plumbing — the biofilm is consuming the sanitizer faster than you can add it. Purge and refill.
• UV degradation — chlorine is destroyed by sunlight. Keep the cover on when not in use.

A realistic weekly time budget

• Monday: 3-minute test and dose (if needed)
• Wednesday: 3-minute test and dose (if needed)
• Friday: 3-minute test, dose, and quick waterline wipe
• Every other Sunday: 5-minute filter rinse

Total: about 15 minutes a week. Anyone selling you more work than that is selling you chemicals you don't need.

When to call a pro

If the water stays cloudy or smelly after a proper drain-and-purge, or if sanitizer won't hold no matter what you do, there's usually a biofilm layer that a home purge can't reach — or an equipment problem (ozonator dead, circulation pump too weak, filter housing bypass). A single diagnostic visit sorts it.

Book a flat-rate maintenance visit and we'll bring your water back to clear in one appointment.