Hot Tub Flush

Strip biofilm from hot tub pipework before a water change. A single 200 ml dose dissolves the slime layer that hides bacteria from your sanitiser and keeps demand high.

• Penetrates and dissolves biofilm inside the pipework and jets.
• Frees trapped body oils, lotions and dead skin.
• Resets sanitiser efficiency for the new water fill.
• Removes the cause of cloudy water that returns within days of a refill.
• Helps tubs pass routine bacterial swab tests.

Sizes and prices

• 1L: £8.99
• 2.5L: £14.93
• 5L: £24.83
• 10L: £44.63
• 20L: £84.24
• 25L: £104.04

When you need it

• It is time for the quarterly water change.
• Sanitiser demand has crept up despite no change in use.
• A musty or sour smell rises from the jets when first switched on.
• Cloudy water keeps returning days after a refill.
• You have just bought a used hot tub of unknown history.

How to use

1. Remove the cartridge filter and put it aside; do not refit until after refill.
2. Pour 200 ml of Hot Tub Flush per 1500 L directly into the tub.
3. Switch the jets on high and run for 30 minutes uncovered.
4. Switch the jets off and leave to soak for 8-12 hours, ideally overnight.
5. Run the jets again for 10 minutes, then drain the tub completely.
6. Wipe the shell, hose down the empty tub, refit a clean filter and refill with fresh water.

Dosing guide

Use only when draining the tub. Increase the soak time, not the dose, for tubs with very heavy biofilm.

• For 1,000 L (small spa), add 150 ml to reach Standard flush.
• For 1,500 L (typical hot tub), add 200 ml to reach Standard flush.
• For 2,000 L (large hot tub), add 300 ml to reach Standard flush.
• For 5,000 L (swim spa), add 750 ml to reach Standard flush.
• For 1,500 L, add 300 ml + 24 h soak to reach Heavy biofilm soak.

How it works

A pH-elevated blend of biodegradable surfactants and chelators designed to penetrate the polysaccharide matrix that bacteria use to anchor themselves inside hot tub pipework.

Biofilm is a slime made of polysaccharides and trapped organics. The flush raises local pH, breaks the polysaccharide bonds and lifts the slime layer off the pipe walls. Once detached the slime is suspended in the water and drained out with it.

Up to 99% of hot tub bacteria live in pipework biofilm, not in the bulk water. Standard refilling does not remove biofilm, so the new water inherits the same demand. A pre-drain flush gives the new fill a clean pipework start and dramatically lowers ongoing sanitiser use.

Frequently asked questions

How often should I flush the pipework?

At every quarterly water change, or after any heavy bather event.

Do I have to remove the filter?

Yes. The filter would be ruined by biofilm release and surfactants. Set it aside and refit a clean one after refill.

How long should the soak be?

8-12 hours overnight is standard. Up to 24 hours for tubs that have not been flushed for years.

How many flushes does 1 L cover?

Five 1500 L flushes at 200 ml per flush.

Is it safe for inflatable hot tubs?

Yes. The flush is safe for vinyl, acrylic and inflatable surfaces when used as directed.

Will it damage my pump or heater?

No. The active dilution is well below thresholds for pump impellers, seals or heater elements.

What is biofilm chemically?

A polysaccharide gel produced by bacteria that anchors them to surfaces and shelters them from sanitiser.

Why can sanitiser not remove biofilm?

Free chlorine and bromine react at the surface and do not penetrate the gel matrix. Specific surfactant chemistry is needed to break the matrix.

Does it raise total dissolved solids?

Briefly, but the entire flush is drained, so the new fill starts at TDS zero.

Lots of foam during the flush?

Expected. Reduce jet speed; foam will subside when jets stop. Drain after the soak.

Smell still present after refill?

Drain a second time and re-flush at the same dose; very neglected tubs sometimes need two cycles.

Sanitiser demand still high after refill?

Replace the filter cartridge and shock the new fill; old filter or unwashed shell carries biofilm forward.

Hot tub flush vs filter cleaner?

Flush cleans pipework biofilm before a water change. Filter cleaner cleans the filter element. Use both at every water change.

Hot tub flush vs household bleach?

Bleach reacts at the surface and rarely penetrates biofilm. The flush uses surfactants and chelators that strip the matrix.