White water mould is a natural fungus that can form in swimming pools, hot tubs, and even your garden hose. It likes to grow in damp areas, so plumbing, pool toys, filters that are reinstalled wet, and even the garden hose make the perfect environment for it to grow. Seeing these white flakes in your water can indicate a bigger mould problem within your plumbing, as well as problems within your water chemistry, so it’s best to act quickly.
What Does White Mould Look Like in Hot Tubs and Pools?
White water mould looks like white flakes floating around the top of your water or along the water line, almost like a shredded, used tissue (it can even be slimy and snotty looking).
Is White Mould Dangerous?
White water mould itself is more gross than toxic, though it does mean your water is likely inadequately sanitized - not good for soaking. However, if this type of mould is left untreated, it will wreak havoc on your hot tub water, if it hasn’t already, and can quickly lead to the formation of pink mould, which is dangerous.
What Causes White Water Mould? Can It Be Prevented?
As we learned earlier, this kind of mold like to live in damp places. With a pool or hot tub, white water mould outbreaks can come from a few places:
Bathers shed skin cells, body oils, lotions, and a variety of personal care products into the water. If adequate bromine and chlorine levels are not consistently maintained, these pollutants are allowed to mix, grow, and an outbreak of mould can occur. Showering (without soap or products) immediately before using the spa can help ease the workload on the filtration system, though sanitizer levels should always be tested and corrected weekly at a minimum.
Adding damp filters or toys to your pool or hot tub water can put it at risk for a mould outbreak. Clean all toys/filters regularly and allow them to dry completely before they go back in the water (ideally under the sun, as UV rays act as a natural oxidizer).
Filling with water from a contaminated garden hose can transfer the mould to your pool/spa water. Examine your hose and nozzle for signs of mould if you think this could be the culprit.
Not regularly cleaning your surface walls, filters, and other components allows mould to breed uninterrupted. Plan for a thorough clean of your spa quarterly (read more on maintenance schedules).
Prevention is key! If you follow these tips and keep up with regular maintenance and care, mould shouldn’t be able to grow within your pool or hot tub.
How Do I Get White Mould Out of My Water?
It’s important to take time and thoroughly clean your pool or hot tub of any white mould, as any microscopic particles left behind can grow back into a massive problem. The process is a bit different for pools as opposed to hot tubs.
Removing White Water Mould from a Hot Tub
Since draining a hot tub is considerably easier than draining a pool, it’s a good idea to flush the mouldy water where weather and situations permit in order to make sure the mould is thoroughly cleaned out. Remember to be meticulous in your cleaning to ensure all mould particles are removed. If any spots of mould are missed, it can regrow out of control again quite rapidly, and you'll be back to square one, so make sure to triple-check your work!
Check that all jets, diverter valves, waterfalls, pipes, and any other water features are fully open and flowing water
Before you start cleaning, take a look at your filters. If they’re newer and in good condition, you can probably just kill the mould on them by doing a chemical filter soak with a filter cleaning agent like the Spa Essentials Filter Cleanser. If they’re over the 1-year mark, looking discoloured or frayed, consider just replacing them. The filter is your first line of defence against bacteria and moulds, so especially right now, you'll need a filter working at optimal strength
Super chlorinate the water to levels of at least 20ppm for a minimum of 72 hours to kill the mould and bacteria. Check the water every 24 hours to ensure adequate levels of chlorine; during these checks, also drain a bit of the super-chlorinated water into the spa drain to ensure no mould is alive down there
After the 72 hours have passed, use a pipe cleaner specifically formulated for spas like Pro-Clean Whirlpool Flush to remove the dead bacteria and slime leftover in the pipes. Generally, the pipe cleaner will need to circulate through your hot tub with the pumps on high speed for at least an hour before draining (always follow the directions on the bottle of the product you're using)
Fully drain all the water out of your spa to remove all the residue from your spa. Give the shell a good scrub while it's empty to remove any stuck-on grime that may have formed using a hot tub cleaner.
Fill the hot tub with fresh water, then circulate shock through the water as you normally would to break down any stubborn biofilm that may be left circulating throughout the plumbing; drain for hopefully the last time.
Fill your spa with fresh water, then power it on while observing the jets to make sure no white flakes are coming out. If you do still see these mould particles, drain the spa and fill it again to flush the plumbing further until you have a spa with clear water.
Put your new/clean and dry filters back into the hot tub.
Chemically balance the water as you normally would after a fresh fill.
Set up a maintenance plan to stay on top of water maintenance! Mould doesn’t show up overnight, so if you’re able to keep a clean spa with balanced water, you should be able to maintain clear and clean water.
Removing White Water Mould From a Pool
You’ll need to shock the pool to kill the mold which can only be done when the sun has gone down, so plan accordingly before starting.
Clean your filtration system as you normally would. There’s likely mould in here, and we’ll want to remove the surface layer of gunk first (we’ll do a more thorough clean later)
Test your pool water and make sure chemical levels are balanced, specifically the pH (don't worry about the sanitizer levels as we're about to super chlorinate, but do make a note of where it's at - inadequate levels could be why the mould formed in the first place)
Shock the pool to super chlorinate the water; you’ll need to use 3-4 times the normal amount of shock to get adequate levels of chlorine to kill off the mold
Clean the surface of your pool using a stiff brush, as well as scrub in all around jets, skimmers, ladders and parts to make sure no mould is lurking around
Leave water to circulate throughout the pool for at least 24 hours to allow for the super chlorination to work and the scrubbed off mould to circulate into the filter
Brush the pool surfaces again; you may have missed some mould particles, or more may have settled back into nooks and crannies while water was circulating. We don’t want to leave any mould particles behind in the pool.
Vacuum the pool manually to thoroughly clean the water; have your garden hose handy to top up if the water line gets too low.
Clean your filter again, this time using a chemical cleaner such as Filter Perfect to deeply clean your filtration media of bacteria.
Test and balance the water. Then test and balance the water again, and again. Ensure pH, alkalinity and chlorine are always strictly within range, and develop a routine maintenance schedule to ensure levels remain consistent so the problem doesn’t repeat.
Watch for white mould in the coming days - it’s possible you missed a spot, even with the most thorough cleaning. Run the pump and clean the pool often, just to ensure no particles are left behind to grow.
Mould is one of the more tedious problems to solve, so preventing it is always the goal. Remember to keep on top of your chemical levels and follow your maintenance routine for beautifully clear, clean water.