Does your spa or hot tub smell? Does it have odors that you just can't get rid of? Let's try to figure this out. More often than not, many spa owners blame the odors on "too much chlorine." Unfortunately, that is rarely the case - especially if you're not using chlorine! Some odors are chemical, some are environmental. Most odors can be successfully treated and cured. Odors can even be prevented with proper maintenance.
Smelly Spa & Hot Tub Odors are caused by:
Tubs
- Improper sanitizer use
- Improper water balance
- Lack of regular maintenance
- Insufficient drain & refill procedures
- Environmental reasons caused by uncontrolled biofilm build up
Chlorine and bromine are both excellent sanitizers used in spas and hot tubs. When they are used, they do breakdown, actually combine with, waste products of what they have sanitized. These wastes are typically in the form of nitrogen and when the nitrogen combines with the chlorine, they become smelly chloramines; when combined with bromine, they become bromamines. The real bad news is that chloramines are virtually worthless at killing bacteria. Bromamines however, are still somewhat effective sanitizers.
Consumer studies have shown that people actually like the smell of chlorine; at least when it's in its useable state! A "fresh" chlorine odor reminds people of cleanliness & sanitary conditions. Chloramines are a different matter especially when further combined with carbon dioxide gassing from the air jets, while also driving up the pH. That's what gives you that acrid or acidic "chlorine" odor that nobody likes. That's one of the "false" reasons people then switch to bromine. But bromine has its own di-stink-t odor (sorry, I couldn't resist).
In order to break up these combined chlorines & bromines, it is necessary to shock the water. Shocking, using additional chlorine or a non-chlorine oxidizer such as potassium mono-persulfate, breaks the chemical bonds. The trick is to allow the waste to fully gas off from the spa water. What happens if the waste is not allowed to gas-off? Chloramines and bromamines recombine with a vengeance. Excess chloramines & bromamines can also lead to "red-eye" (tear gas is a form of chloramine). You won't only smell the problem, different parts of your body will feel the problem.
The gassing-off process is simple: after shocking, leave the spa cover off of the spa for at least 1 - 2 hours (ideally). If the waste is not fully allowed to gas-off, the waste chloramines and bromamines literally hit the underside of the spa cover and fall back into the water! Even if your spa is not regularly used, it is an excellent idea to remove the cover for at least one hour weekly to let the "bad air" gas-off.
Keep in mind that as similar thing happens with an indoor spa thereby requiring good & constant ventilation especially while the spa is being used. The condition can become worse as the waste gasses and un-oxidized bacteria are aerosolized into the room. People with asthma or other breathing trouble can experience a condition known as "hot tub lung."
We sometimes hear of customers noting similar "choking" odors when using biguanides such as BaquaSpa or Soft Soak or Leisure Time Free. A similar scenario is taking place: "used" biguanide molecules with attached wastes are being aerosolized out of the spa and into your face! Proper shocking with the hydrogen peroxide shock is necessary on a weekly basis to break up this un-filterable waste. Don't be afraid to double or triple shock. Do NOT however, use swimming pool hydrogen peroxide - the odor will be worse. Only use spa formulated biguanide products.
Poor water balance - especially very low or high pH - will affect the chlorine & bromine levels leading to chloramines and bromamines as mentioned above. Low pH (under 7.0) can cause the water to give off very acidic gases leading to coughing, wheezing or other health problems. Water having a High pH (over 7.8) can lead to stale & funky smells plus additional scaling.
Regular maintenance of your spa includes periodic (weekly at least) cleaning or wiping down of the spa surfaces (waterline, pillow areas, drink-cup rests, etc). This wiping also aids in removing the biofilm build-up on visible areas. Further regular cleaning involves cleaning the filter (chemically cleaning, not just rinsing) and cleaning the inside of the spa cover (monthly spray of Pristine) helps kill mold & mildew that grow in or on the insulating foam.
Draining & refilling of your spa or hot tub on a regular basis is the simplest, single best thing you can do to control odors. Be sure to know often to drain & refill; this varies with spa size, use, time of year, parties, even showering BEFORE using the spa. Typically every 4 to 12 weeks is good. Smaller 2 person spas normally need more frequent water changes than larger 8 person spas (except if 8 people are using the spa more than twice a week!). Take a look at our article about Purging, Draining & Refilling. Following that formula be sure to Purge (removes biofilm build-up), Drain, Clean (all surfaces & filter), and Refill.
Environmental reasons for spa & hot tub odors are due to the build-up of bio-films on spa surfaces and plumbing lines that contribute to the formation of White Water Mold and Pink Slime and all of their odors. As biofilms build, multiply, and spread throughout the spa system, odors worsen dramatically. For that reason it is almost mandatory to use plumbing line cleaning products such as Spa System Flush or Spa Purge.
Enzymes can further help prevent and eliminate odors by "eating" or consuming much of the greases, body oils and waste that interfere with whatever type of sanitizing system you use. With a little effort (no more than 15 - 20 minutes each week) you can effectively control and even eliminate odors in your spa.
Treating Smelly Hot Tubs