5 Possible Reasons Your Hot Tub Is Foamy (and How to Fix It)

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If you own a hot tub, you know that one of the most annoying things that can happen is when foam starts to collect on the surface—especially when it's that slimy, green kind that doesn't smell too great either.

Not only is it unsightly, but in some cases it can also make it unhygienic to enjoy your hot tub. But don't worry, once you identify the cause of the foam, there's usually a simple fix to get rid of the problem.

What causes foam in hot tubs?

There are a few common causes of spa foam, ranging from poor water care to unintentionally introducing a detergent. Let's take a look at how to identify what's causing yours.

Improper water balance

If the sanitizer levels in your hot tub are too low, it can cause foam to form. This is because there are not enough chemicals (usually chlorine or bromine) present to properly break down the organic matter in the water, which can lead to an increase in the amount of bacteria and other contaminants.

In addition, low sanitizer levels can also cause the water to become cloudy and difficult to see through. A telltale sign that this is your problem is if the foam is slimy, sticky, or has a bad smell.

You can check for sure using some test strips, and adjusting the levels as needed:

  • If using chlorine, it should measure between 1.0-4.0 ppm
  • If using bromine, aim for 2.0-6.0 ppm

To maintain a healthy water balance in general, you want to aim for these readings:

  • pH between 7.2 and 7.8
  • Total alkalinity between 80 and 140
  • Calcium hardness between 150 and 250

Personal care products

Cosmetic products like soaps, lotions, shampoo, and conditioner, are another common cause of foam in hot tubs. This is because these products contain surfactants, which are great when you're lathering up in the shower—but not so great if they make it into your spa.

It's really important to properly rinse these products off after showering, and ideally shower before using the hot tub too. Because of how hot tub water gets circulated vigorously by the jets, even trace amounts of foamy products that make it in can be enough to wreak havoc in your spa.

Swimsuits

Just like how things like shampoo and body wash can cause foam if they make it into the spa, the same can happen with detergent on improperly rinsed swimsuits.

When this detergent comes into contact with the water, it could once again cause foaming issues. That said, laundry detergent is somewhat less likely to cause a large amount of foam than personal care products.

Check out some more tips for minimizing this problem if you think this could be the culprit.

Beverages

There's nothing like kicking back in the hot tub with a nice cold beer, and we all like to keep drinks and snacks nearby. But unfortunately, spilled or splashed beverages could be the cause of foam in your hot tub. Sugary drinks especially could also breed bacteria in the water if your sanitizer is struggling to keep up.

If you think this might be what's happening, you can either stick to plain water, switch to a sippy cup, or perhaps invest in a better hot tub drinks holder. This way you'll have somewhere secure to keep your drink without fear of it mixing the the spa water.

Non spa-safe fragrances

A little fragrance can be a magical addition to a hot tub, but never be tempted to add regular bath bombs or bubble bath. These are a sure-fire way to cause foam issues in a spa.

You'll be pleased to know that there are spa-safe fragrances you CAN put in your hot tub. These are specially designed to not produce foam, so you can also run the jets safely.

So, leave the bubbles for the bathtub and stick to spa-safe alternatives if you like to soak in a scented spa.

How do I get rid of foam in a hot tub?

Alright, so you have foam in your spa, and hopefully by now you have a better idea of the root cause. But what can you do to fix the problem right now?

Quick fix: anti-foam chemicals

In a pinch, there are products you can add that will help to neutralize the foam:

SpaGuard Spa Anti Foam, 1 Pint
SpaGuard Spa Anti Foam, 1 Pint
View on Amazon

These are chemicals that can help as a quick fix in the short term, but it's always best to fix the underlying problem as well if you want to prevent the foam from coming back.

Long-term fix: drain and refill

If you've tried everything and you still can't seem to banish the foam, the last resort is going to be a full drain and refill, so you can start again with fresh water.

If you've been struggling with foam, chances are you may also have bacteria living in the pipes. For this reason, it's a good idea to do a full line flush so your effort isn't wasted.

Once your spa is back to sparkling, try to stay on top of maintenance to avoid the foam problem coming back.

I have a free printable hot tub maintenance schedule which you can download to remind you of exactly what to do.

How to prevent hot tub foam

To summarize, the first step in preventing that inconvenient hot tub foam is to identify why it's happening in your spa. A dirty, unbalanced spa will call for a different fix than one that has trace amounts of shampoo in it.

Once you've done that, you can try a quick fix of some anti-foam while you plan how to get your spa water back to a foam-free state. Depending on your issue, be aware you may be looking at a full drain-and-refill to restore your spa water to its original cleanliness.

To prevent the foam from coming back in the long term, be sure to keep your water properly balanced (sanitizer especially), take care not to introduce foaming contaminants either on yourself or your bathing suit, and always stick to spa-safe products if you like to add any kind of fragrance during your spa sessions.

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