How to Unfreeze and Empty an RV Holding Tank

An RV by a lake
  • 2-10 hours
  • Beginner
  • 10-60
What You'll Need
Gloves plastic or rubber and disposable
Safety Glasses
Hair Dryer (Blow Dryer)
Absorbent Cloths
Bio Based Antifreeze
Standard Toolkit

A RV holding tank holds fresh and waste water. If the temperature is cold enough the water freezes in a normal circumstance but the RV's radiator has anti-freeze to prevent this. This is of course toxic and fresh water must never be mixed with your RV’s anti-freeze.

There are three RV holding tanks: fresh, black, and grey. These are for drinking water, toilet water and kitchen sink water. Let’s find out how to unfreeze and empty an RV holding tank.

Step 1 – Preparation

First the RV needs to be under cover so that the temperature will be above freezing. You’ll need a suitably covered area, for example a large garage and the ability to gain access to the underneath of the vehicle. Put on your safety glasses and gloves to protect the eyes and hands.

Step 2 – Locate the Tank

Check your RV’s manual for the location of these holding tanks. They are generally located under the RV and close together.

Step 3 - Clean the Tank

Clean off any accumulated debris from the RV holding tank. Use can use warm soapy water and a cloth for the purpose.

Step 4 – Provide Heat

Plug in the hair or blow dryer and direct the warm air towards the RV holding tank. Keep 6 to 12 inches in distance from the holding tank and keep moving the dryer back and forth, up and down, and in a slow, but constantly moving sweeping motion. Be careful not to remain on one spot for too long as this could damage or melt the plastic material of the tank and pipes. Don’t allow the dryer to overheat.

Step 5 – Check

While doing this, check that the ice which formed in the tank has not split the tank or pipes connecting to it and they are not damaged or leaking. Check that the securing rings connecting the pipes to the tanks are fully tightened and undamaged also.

If damage has occurred to the RV holding tank or any of the connections or pipes you’ll need to replace them, as repairs are not usually possible. If this is the case, stop the attempt to defrost the tank or tanks and purchase replacements; then you can detach the faulty items and replace them. Once this is complete, continue to unfreeze any tanks that are still in need of attention.

Repeat this process for each of the three holding tanks.

Step 6 – Empty the Unfrozen Holding Tanks

Once the tanks are unfrozen, drive to an RV waste dumping station. Empty each in this order: first black, then grey, then finally the stale fresh water.

Step 7 – Replace

Replace with water and a non-toxic additive which acts as an anti-freeze and is commonly available: bio-based additive is safe for humans to drink. Add to each holding tank. This should ensure that even though temperatures may continue to remain below freezing, each RV holding tank will remain ice free and fully functioning.