There’s a time for everything – a time to exercise in your swim spa, a time to invite friends for a swim spa party, a time to add FROG Maintain^®, your monthly non-chlorine shock, and eventually, a time to purge.

While purging your swim spa doesn’t top the “Fun things to do this weekend list,” it does top the “Glad I did it and I love my swim spa even more” list.

Purging may seem daunting, but it can be easy, especially if you know:

• Why you need to purge

• When to purge

• How to purge

Why purge your swim spa?

Even if your water and sanitizer levels are in the ideal range, your swim spa can develop biofilm over time inside the pipes.

Biofilm is made up of living, reproducing microorganisms, like bacteria. They form communities called biofilms. They make a sticky substance that holds them together. Different bacteria use different methods to form these communities, which depend on the environment and their specific characteristics.

Biofilm can form in the swim spa’s pipes and plumbing system, so you can’t see it.

Many swim spas have more than 100 feet of pipe – that’s potentially a lot of biofilm.

If left untouched, biofilm builds up and becomes more and more resistant to any sanitizer. 

Blood, sweat and tears

The average person also contributes waste such as blood, sweat, tears, urine, saliva, mucous and other bodily fluids. But that’s not all.

Personal care products – lotion, soap, deodorants, makeup, hair products, and perfumes – all dissolve off skin and hair and into the swim spa water.

The Environmental Working Group reports that the average adult in 2023 uses 12 personal care products each day with 112 unique ingredients. Most of these personal care products are shed into the swim spa water upon immersion.

It’s almost impossible to test for and identify biofilm, since it’s nearly microscopic in its early stages.

Biofilm:

• Consumes sanitizer, affects pH and water balance

• Can harbor harmful bacteria colonies

• Causes foam and other water problems

• Reduces pipe diameter in acute cases

Biofilm is a problem because it consumes chlorine and can harbor harmful bacteria. Once biofilm forms, it’s difficult to remove even with increased sanitizer or shock treatments.

Now for the good news

Biofilm is removable (in most cases) and preventable. With proper purging, your swim spa water will be crystal clean and clear for months.

What swim spas are susceptible to biofilm?

Short answer: all swim spas, including those that are well-maintained. However, some swim spas can be more susceptible sooner:

• New swim spas

• Swim spas used a lot – many times a week, and/or are used by many people – if sanitizers and filters are not maintained well

• Swim spas that are not maintained well – for example, with old, used filter cartridges, or incorrect or inconsistent use of sanitizers, and not shocked routinely

• Unused swim spas – full of water, or even drained (water can be in the pipes)

How do you know when it’s time to purge?

A best practice is to purge your swim spa when you first purchase it.

Swim spas are “wet tested” at the factory.  Wet Testing is when a swim spa is filled with water and run to make sure there are no leaks.

The swim spas are drained, but not blown out, meaning that water is in the plumbing for weeks, maybe months before the swim spa is sold and placed in a consumer’s backyard.  This allows for plenty of time to grow biofilm in the pipes.

It’s ideal to purge your swim spa each time before you drain and refill it.

Purging typically works best when the water is hot – that’s the best time to get all the biofilm and any other buildup out of the pipes and plumbing.  Purging every time you drain and refill your swim spa will allow your swim spa to be its most efficient and ensure that your sanitizer works to kill fresh bacteria introduced into the water – not existing or growing bacteria inside the plumbing.

If you don’t purge each time you drain and refill your swim spa, some signs that biofilm buildup is becoming too much for sanitizers and regular shock include:

• Inability to get rid of foamy or cloudy water no matter what you try

• Inability to balance the water’s pH

• Use of more and more chemicals than usual

• Bad smelling or off-color water

• A noticeable buildup of scale around your swim spa

• Film or slime on the water surface or other surfaces

When it’s time to purge

Follow three main steps – shock, purge and drain. You and your swim spa will be happy in no time:

To purge, start with shock

Shocking is part of the purge process. Use a purge product that’s designed to flush biofilm and contaminants out of the pipes. Before draining, add a shock to kill bacteria.

You may want to flush out the pipes with a flush product formulated to clear all bacteria, biofilm buildup and contaminants.

This is a good time to ask your retailer what products they recommend. Follow manufacturer’s directions on the product(s) you use.

Warning: You’ll likely notice some nasty looking foam, ugly looking water and gunk. That’s good news – you’re getting rid of it! You can remove a lot of it with a small surface skimmer.

Purge

Use a purging additive to remove accumulations from the surface and the swim spa’s plumbing lines. Allow it to circulate through the spa overnight to ensure the biofilm is stripped away from the lines. This is essential.

Failing to purge the plumbing lines will allow the biofilm buildup to circulate back through the swim spa water over and over again.

Drain

Once you’ve finished the purge process, shut off your swim spa. Drain the water from your swim spa, following the directions in your swim spa owner’s manual. You can always ask your retailer for help.

While the water is draining, clean the filter – follow directions on the product you use to clean it; most call for a 24-hour soak.

Or replace the swim spa filter cartridge to ensure that bacteria is not hiding deep in the pleats of the spa filter.

Expert Tips:

Use a submersible pump (sump pump), placed in the deepest part of the swim spa. Plug it in and turn it on. Turn it off when the water is drained – if it runs dry the motor can burn.

Use a wet/dry vacuum or spa wand to drain any remaining water.

When the water has been drained, clean every surface of the swim spa with cleaner your retailer recommends.

Clean swim spa pillows, rails, the water line, inside and around the jets, rails, steps, the sides, and surfaces of the spa to remove any persistent biofilm. Leave no surface behind!

Give the swim spa a final, thorough rinse with a hose, then drain it again.

A final rinse will get rid of any residual cleaner, which can cause foam when you refill the swim spa – then you’ll have to drain again. And that’s a draining experience! 

Refill the swim spa with fresh water. Test it for metals, adjust if needed. Follow the start-up routine your sanitizer product or swim spa retailer recommends to balance your water, and then add your sanitizer.

Expert advice

If you use FROG^® @ease^®, you can maintain clean, clear water longer than the usual 3 months that is most often recommended for draining and refilling your swim spa.

That’s because FROG @ease uses up to 75% less chlorine*. FROG @ease contains no cyanuric acid, so there’s no buildup. And it kills bacteria 2 ways – with SmartChlor^®, a unique, patented chlorine and sanitizing minerals.

Replace the FROG Minerals every 4 months, they work in conjunction with SmartChlor to keep the water clean and crystal clear.

Interested in FROG @ease? See this video for easy swim spa start-up directions:

Sources:

Cs.montana.edu A Brief Introduction to Biofilms

ewg.org Survey finds use of personal care products up since 2004 – what that means for your health

*Compared to the minimum ANSI recommended chlorine level of 2.0 ppm for a swim spa.