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How to Cure Chlorine Demand and Chlorine Lock in a Hot Tub

Does your hot tub continue to demand more and more chlorine and do you have a chemical smell in and around your hot tub? If so, you could be experiencing chlorine demand or chlorine lock issues with your spa.

How to Cure Chlorine Demand and Chlorine Lock in a Hot Tub

Today, let’s find out exactly what chlorine and demand and chlorine lock are and what you can do as a hot tub owner to deal with the problems if you run into chlorine demand issues with your spa.

What Is Chlorine Demand and Chlorine Lock?

Chlorine demand is simply the measure of how much chlorine is needed in your hot tub in order to properly sanitize the water and remove not only contaminants, but also irritating chloramines from the water. If you are wondering how you find out what your chlorine demand is, there are tests for that!

Lamotte 3366-01 Pool MGR Test Kit, 0.2-3.0 ppm Free/Total Chlorine, 6.8-8.2 pH Range, 60-400 ppm Total Alkalinity, 60-400 ppm Calcium Hardness, Acid Demand

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In theory, chlorine lock means that there is too much stabilizer in your hot tub that prevents your chlorine from oxidizing your spa water properly. However, in practice, this just doesn’t happen. In fact, in most cases, the terms of chlorine lock and chlorine demand are used interchangeable by pool and spa experts today. The fact is that most problems aren’t really locks but heavy chlorine demand.

In some cases, your chlorine demand may remain high no matter what you do. This is when it can become a problem. However, like so many hot tub issues, there are solutions out there that are easy for you to do yourself.

Causes of Chlorine Demand and Chlorine Lock

There are many reasons that your hot tub could be demanding more chlorine than normal. If it is outside, weather such as heavy rain can cause your hot tub to need more chlorine than normal.

If you keep it covered or if it is inside, then chances are you have biofilms or other contaminants present in the water. Remember, the warm hot tub water is the perfect environment for many bacteria. These bacteria can cause a demand spike in your chlorine especially if they have infested your plumbing.

How to Cure Chlorine Demand and Chlorine Lock

Is your hot tub demanding chlorine? If so, then all you need to do is give it what it needs. Try shocking your hot tub to give it the boost it needs to properly oxidize any contaminants in the water. Sometimes, you may need to shock it more than once to take care of that chlorine demand once and for all.

Remember, chlorine lock isn’t a real thing, but many pool and spa experts still use the two terms interchangeably. That means that no matter what they say, they are really talking about the amount of chlorine your hot tub needs to oxidize the contaminants present in the water.

Sometimes, no amount of shock will take care of your chlorine demand problem. When this happens, chances are you have biofilms or other contaminants in the plumbing system of your hot tub. When this happens, your only option is to drain the hot tub and clean the sides and plumbing of your spa thoroughly before you refill it and add your sanitizer.

Keeping Chlorine Demand In Check

Regular maintenance is the key to keeping chlorine demand in check. Regularly test your water and make sure all your sanitizer levels, pH levels, TA levels and calcium hardness levels are in their proper range. Regularly shock your hot tub and clean the filter to ensure that the plumbing stays clean. Periodically, drain your hot tub and give it a thorough cleaning.

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If you do this, you will reduce the chance of developing a chlorine demand problem in your spa. However, just because you keep your hot tub chemistry perfectly, doesn’t mean it won’t happen to you. If it does, just take the proper steps to put a stop to the demand before it gets out of control.

Parting Thoughts

Chlorine demand and chlorine locks can be a headache for hot tub owners. In some cases, you can do everything right and still have to deal with the problem of chlorine demand. Still, like most problems, there are methods to getting rid of chlorine demand. Sometimes, you may have to drain your water and start over, but the problem can still be easily remedied.

Hot Tub Chemistry 101

Keeping your hot tub chemistry in check is not only important for your tub, but also for the people in it. Check out our complete guide to hot tub care.

If you are experience problems with chlorine demand, don’t ignore the problem. The longer you let it go, the worse it will be. In the end, with a little shock and elbow grease, you can get your chlorine demand under control before you really start experiencing problems with your water quality.

Happy Soaking!

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Last Updated: Tuesday, February 7th, 2017