How Do You Flush Antifreeze Out of a Hot Tub?

Filling your tub’s pipes with antifreeze is a mandatory step in winterizing your hot tub. Antifreeze can be toxic as well, so getting the right type of antifreeze is crucial. After that, you’re done for the winters until it is time to reopen your hot tub. That’s when you must build up towards draining antifreeze from the system.

To flush antifreeze out of a hot tub, you need to spray water into the tub’s interior and let the water drain out. It will take antifreeze out of the system, given that there are no blockages. To prevent resistance, you can add bleach to the mixture and let it sit for a while before flushing.

In this article, you will discover all the steps you must take before and after flushing antifreeze out of your hot tub. By the end, you will know how to safely reopen your hot tub after winters. Moreover, you will also find out whether winterizing your pool is necessary or worth it and if there are any alternatives. Now, let’s start with the steps you came here to learn.

Test valves and plumbing unions for tightness

The goal of flushing antifreeze isn’t just to get rid of antifreeze but is to make room for water. While leaky plumbing is okay for flushing out antifreeze, you need to ensure that valves and plumbing unions are tight before you pour water into your hot tub. Therefore, the first step is to carefully test vales and unions for leakage. 

The unions are the heater manifold, and pumps need to be looked at quite carefully. As for valves, the ones likely to have tightness problems are the drain valves as well as the knife vales. If the levels of antifreeze seem lower than they were when you first poured it, then you should assume there are leaks. 

Again, leaks don’t cause problems when it comes to draining antifreeze. If anything, they actually help. However, they prevent you from adding water to the tub after you flush out the antifreeze.

Add bleach to the antifreeze

This isn’t a mandatory step as any opening in the tub’s system will drain out the antifreeze. However, adding bleach will have a thinning effect and will make it easier for antifreeze to get flushed out. 

More importantly, the bleach will clean out minor debree in the plumbing. If dust has consolidated into clusters that can block the drainage process, having one part bleach in 10 parts of antifreeze will help dissolve the clumps of dust and clay alongside other contaminants. It is important not to immediately flush the antifreeze right after adding bleach. Let the thinner do its work for at least one hour. Depending on how big your hot tub is, this can take more time as well.

Spray the tub’s interior with water

A strong jet aimed at the seats helps mobilize the impurities sitting in the tub’s interior. You can alternatively use a wet rag to wipe the seats. You’ll still need water to push out antifreeze, which is why using it to clean the tub is a smart choice. 

Once you’re satisfied, you can simply let the water drain completely from the pool. It will flush the antifreeze as well. To be even safer, you can spray more water with a hose directly into the hot tub and pressure-wash the interior, letting the water flow out the drain. This will remove the remaining traces of antifreeze from the tub’s system.

What to do when you have flushed out antifreeze.

Upon flushing antifreeze, your hot tub is ready to be filled with water and can be used again. However, a few problems can occur when filling the pool, which is why it is wiser to take a few precautions. In this section, we will discuss what one needs to look for before refilling a hot tub.


An airlock is a phenomenon where the air gets trapped in a system, and a motor or pump that’s supposed to pull liquid starts pulling air instead. The mechanism doesn’t work when this happens. You’ll detect the overlock automatically when the pump starts, but there is no water flow. In such an instance, you should spot the highest union in the pump and loosen it to let the air come out.

Debris and dirt 

If your hot tub wasn’t covered properly, there might be dirt and impurities in the tub. When liquids circulate through the system, the residue can get pushed into finer plumbing, creating blockages. Using a sifter and a protective grill can keep this from happening.

Chemical imbalance 

From detergents to bleach, lots of different substances can be used in the process following the antifreeze flush. It is crucial to check the pH of the water and take multiple readings as you add pool chemicals to make the water safe to use. Do not rely on previous quantities for at least the first two times you add any chemicals to the hot tub.

Winterizing the hot tub: necessary or not?

You may have to winterize your hot tub depending on the area you live in, but it isn’t universally mandatory. Remember, some of the resources you access were written by people living in freezing states. That doesn’t mean the same applies to you in a coastal location. 

Here, you should use your own judgment: if the winter lasts less than six weeks and the extra electricity the tub consumes during winters isn’t over $50 per month, you should not only keep the hot tub running but must probably use it during the winters. Check out my post on hot tub winter use for more on that.

Final Thoughts

Flushing out antifreeze is step one is reclaiming your hot tub from chilling winters. You can approach this with a straightforward nail-on-the-head strategy and simply let the stuff drain out while you pressure wash your hot tub, or you can take some additional steps to prevent inconvenience down the line. You can also choose to take a few steps after you flush out the antifreeze to avoid damaging your tub’s heat pump and fine plumbing.

Jed Arnold

Jed spent every year from the ages of 15 - 22 as a Lifeguard (Red Cross) and ages of 17 - 22 as a Certified Pool Operator (CPO). Between working for over a dozen facilities and owning a pool, he carries over a decade of pool experience.

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