The first thing that comes to mind is “ewww!” No one wants to get in a body of water that smells like mold. Hot tub mold is not exactly the most inviting, come and relax scent, but unfortunately it can be a common problem for hot tub owners.
The first thing to do when you are getting a bad hot tub mold smell from your water is check your chemicals. Moist, warm, humid places like a hot tub can be a breeding ground from bacteria, keeping proper water chemistry is the key to avoiding bacteria and ensuring your water stays clean and safe for bathers.Completing regular water tests will help you make sure that chemicals are maintained properly.
If your water has been neglected for a while and you are having foul odors it is possible that you also have bacteria built up in your plumbing and filter. The best way to correct the problem is by decontaminating.
To do this, you will want to give your spa cover a thorough cleaning as that is a common place for bacteria build up and mold formation. If your hot tub cover is in less than stellar condition or water logged it might be time to consider a new cover as you do not want bacteria being harbored in your old one.
Also you will want to remove and inspect your hot tub filter as bacteria and mold can build up in the filtration system and cause a foul odor.If your filter is more than a year old or in bad condition it is best to replace it, otherwise make sure you are cleaning it regularly with filter cleaner to avoid bacteria build up and ensure that your filtration system is clean and able to do its job properly.
The next step in decontamination and getting your water back in good condition is to hyper chlorinate. Hyper chlorination will give your spa water an extra dose of sanitizer to help kill the bacteria in it.To hyper chlorinate you will want to bring your chlorine level in the spa to a high of at least 100 ppm using granular chlorine.It is best to dissolve the granular chlorine in a 5 gallon bucket of water first so that the granules do not damage your acrylic spa surface.After adding the chlorine to your spa you will want to circulate the water on high speed for a half hour with the cover closed and all jets turned on to get the highest circulation possible.
After hyper chlorinating, prior to emptying your spa you will want to use Spa Purge, this will clean out any other contaminant build up in your plumbing, jets, and filtration system.After completing the purge process it is now time to empty your spa water and refill with fresh water.
Once you have refilled the spa, make sure that pH and Total Alkalinity are balanced. Once you have done that add enough granular chlorine (pre dissolved like before) to bring the level to 10 ppm.Now allow the water to circulate, covered, for 8-12 hours.Now using test strips, like Aquachek Chlorine Test Strips, check the chlorine level.If you get a free chlorine reading then your decontamination was probably a success, if not and the test strips are showing no chlorine reading there is still a high demand for chlorine and the process will need to be repeated.
Once you have tested and come back with a reading that shows a successful decontamination it is time to balance your water with your sanitizer of choice and proceed with regular spa use and proper maintenance.
Keeping on top of regular maintenance by testing and changing your water regularly will help you avoid water problems in the future and hopefully those awful smells that brought you here in the first place.