Short answer: An oily film is most often cosmetics, sweat, sunscreen or grease from the filter. Remove it from the surface, clean the filter and improve hygiene before bathing.
People often assume a greasy coating is a chemical problem. In most home hot tubs and pools, though, it comes from what people bring into the water.
How to identify the cause
- A rainbow-colored or greasy film on the surface.
- A greasy line on the wall.
- Foam when the jets turn on.
- The filter is slippery or dirty.
What to do now
- Remove the film from the surface with an absorbent sponge or skimmer.
- Wipe the waterline.
- Clean the grease out of the filter.
- Test pH and disinfectant level.
- If it keeps happening, consider changing the water.
When it’s better not to bathe
- When the water smells.
- When the film is heavy and greasy.
- When disinfection is low.
Prevention
- Shower before bathing.
- Limit lotions right before using the hot tub.
- Clean grease out of the filter regularly.
- Treat the hot tub right after each use.
When to call a service technician
A service call is worthwhile if grease appears without the hot tub being used; it could be residue in the piping or the equipment.
FAQ
Is an oily film dangerous?
On its own it isn’t necessarily acutely dangerous, but it degrades the water, consumes disinfectant, and encourages foam.
Will more chlorine help?
It won’t remove grease from the filter or surface. Mechanical cleaning has to come first.
Sources
- CDC – water testing in home pools and hot tubs
- CDC – hot tub safety
- Modrá střecha – pool discussion forum (Czech)
- Reddit r/hottub – common questions from hot tub owners
- Trouble Free Pool – community pool water advice
- ALBIXON – most common pool water problems
- ARIVA – green pool water
- Upravvodu.cz – pool water problems
- Laboratoř Monitoring – hot tub water treatment
Next step
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