Is your hot tub as clean? Could it use another deep cleaning?

Download our FREE guide to help you clean your hot tub so it feels like brand new. Just enter your email address to download the guide today!

We respect your privacy and you can unsubscribe at any time. Join 63,666 other hot tub owners.

Get our FREE Weekly Hot Tub Care Newsletter

Sign up for a free weekly newsletter to help you take care of your hot tub or swim spa.

We respect your privacy and you can unsubscribe at any time. Join 63,666 other hot tub owners.

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

Click here to get our FREE weekly hot tub maintenance newsletter!

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

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

List Price:  $89.75
Price:  $89.75
You Save:  

Buy Now On Amazon

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.

Hot Tub Things Oxidizing Spa Shock 2.2 Pounds - Prevents Organic Buildup and Cloudy Water

Hot Tub Things Oxidizing Spa Shock 2.2 Pounds - Prevents Organic Buildup and Cloudy Water

List Price:  $25.26
Price:  $25.26
You Save:  

Buy Now On Amazon

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.

If you are experiencing 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!

Recommended Reading

How to Convert to a Salt Water Hot Tub
Find out what you need to do to ditch that chemical chlorine and convert to a salt water hot tub for your chlorine generation.
Chlorine Versus Bromine: Choose The Right Hot Tub Sanitizer
Which is better? Chlorine versus bromine? This article walks you through each sanitizer so you can decide which one will be best for your hot tub.
A Quick and Easy Guide to Hot Tub Ozonators
This quick guide to hot tub ozonators will give you all that you need to know to maintain your hot tub.
How to Shock a Hot Tub
Find out everything you need to know when you shock a hot tub so you can do it safely and effectively.

The Hot Tub Handbook

Learn How to Keep Your Hot Tub Clean and Clear All Year Long with This Illustrated eBook

You'll save $100 right away with this easy-to-follow digital handbook. This is the guide that hot tub manufacturer doesn’t provide you.

Click here to learn more

Last Updated: Tuesday, February 7th, 2017