How to Unfreeze a Frozen Holding Tank for RVs?

An RV is nothing less than a home on wheels, which means, it has everything you would expect between the 4 walls of your home. To supply you with fresh water for drinking, showering, and other purposes, an RV comes fitted with different water storage tanks.

Needless to say that when the mercury drops below zero, the water that’s left in the holding tanks of your RV would start to freeze. Not only does this renders these tanks useless, but it can also damage the piping and other metal parts underneath the RV.

It is important that you either don’t let this water freeze or unfreeze it if you forgot to empty the tanks before leaving your RV to sit. If you have no idea how to unfreeze a frozen holding tank for RVs, you’re in luck, we have compiled everything to help you with your RV’s holding tanks.

How Many Holding Tanks Does an RV has?

Every RV has 3 types of holding tanks, namely a freshwater tank, a grey water tank, and a black water tank. As the name tells, the freshwater tank contains water that’s safe for human consumption and cooking purposes. The grey water tank receives water that is used for dishwashing and laundry if required.

Lastly, the black water tank gets toilet waste and wastewater from the RV, so you don’t have to worry about dumping the waste.

A Step by Step Guide to Unfreezing a Frozen RV Holding Tank

Grab your gloves, goggles, and other gear, and let’s unfreeze the stale frozen water in your RV’s holding tanks.

Prep the Area and your RV
Park your RV in an area that’s not exposed to the outside temperature, and you can easily move around while clearing the tanks. A large shed or some indoor parking area is a great option, especially where you can safely park your RV and get underneath it comfortably for easier access to holding tanks and performing the procedure.
Find the Water Tanks on your RV
The ideal way to locate the holding tank on your RV is to go through the owner’s manual and find the exact location. Mostly, it is located on the rear side of the RV, underneath the body, and next to the spare wheel.
Clean the Holding Tank
Before you defreeze the frozen holding tank for RV, it is important that you clean it and get rid of any sludge or debris that’d been sitting there for some time now. This makes flushing easier and prevents the pipelines from clogging.
Provide Heat to the Tank
This is the main step where you actually melt the frozen water inside the holding tanks of your RV and try to get rid of it. Make sure that you’ve engaged the parking brake on your RV and a huge container is placed under the outlet of the tank.

Get a blow dryer and provide heat to the tank momentarily. Do not keep the dryer too close to the tank as it could melt the plastic or cause the nearby wiring to catch fire. Keep in 8-12 inches away and provide equal heat to all the areas of the holding tank.

You could speed up the process of melting the frozen water by adding antifreeze to the holding tank, but in a small amount to prevent contamination of the ground. You could also add salt water to the tank that would defreeze it and help you complete your project quicker. If both of these methods don’t help much, bring boiling water with you in a kettle and pour it into the holding tank.

Once the frozen slab of water inside the tank starts melting, you should check the container for progress.
Check for any Damage and Leaks
If the water doesn’t go directly into the container placed underneath the tank and drips elsewhere, there is probably a leak in the pipes, or seals in the system are damaged. You should also check other connections and hoses for any cracks or damaged areas and mark them for repair afterward.
Empty and Flush the Tank
Once the frozen sludge has completely melted, pour in fresh water and get rid of all the remaining residue inside the holding tank of your RV. You should also use a detergent, mixed with an antibacterial solution for flushing the tanks. Not only does it get rid of stubborn debris and deposits inside, but the colonies of bacteria are also cleared along with it. Providing you with a fresh new area to store water for the next trip.


There’s no harm in flushing the holding tank with detergent, rather it cleans the area better and makes sure there are no remnants or debris left behind.

The holding tanks on an RV should be cleaned in the following sequence:

  1. Black water tank
  2. Grey water tank
  3. Fresh water tank

You should not use antifreeze in the holding tank, as it could get mixed with the freshwater which is highly dangerous for human consumption. Moreover, it could also get duped on the ground and it is not safe for the environment.

If the normal unfreezing method doesn’t work, you could add it in a very small quantity to the holding tank.

All the modern RVs have 3 different types of holding tanks, each of which serves a different purpose. If you leave your RV to sit after a trip and don’t flush its tanks, it is highly probable that water will freeze in the winter.

You could unfreeze a frozen holding tank for RV by using a simple home appliance and get it flushed for the next use. It is imperative that you don’t use any hazardous chemicals for speeding up the cleaning and rather use conventional techniques to get rid of the frozen sludge.

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