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How Do I Unfreeze My RV's Grey Water Tank?

by Garry

How To Unfreeze an RV Holding Tank

How To Unfreeze an RV Holding Tank

Help our gray water tank has frozen what can I do?

ANSWER: Greetings Garry thanks for submitting your question on our Ask An RV Question Page.

You do not tell me how full your Grey Water Tank is. If your Grey Water Holding Tank is completely full Option 1 may not work, but still give it a shot then skip to option 2.

Option 1 Partially Filled Grey or Black Water Holding Tank

You will need at least 3 gallons of RV Holding Tank Antifreeze. Start by pouring a 1/2 gallon of antifreeze down the bathroom sink drain, the shower drain and the kitchen sink drain. Once you have done that you need to pour about 1/2 gallon of boiling water down each of the three drains mentioned above. Then again pour another 1/2 gallon of RV Holding Tank Antifreeze down each of the drains.

If you have a motorhome, you may want to drive it around for at least 30 minutes to circulate the antifreeze inside the holding tank. If you have a trailer; or if it is not possible to drive the motorhome let the antifreeze sit in the holding tank for at least two hours, before attempting to dump the tank.

Special Note If Holding Tank Dump Valve is frozen You can use a Hair Dryer on high setting to melt ice and free up the dump valve. Once the tank has been dumped, you need to Winterize Your RV.

Option 2 for a completely full holding tank

You need to get as much RV Holding Tank Antifreeze into the holding tank as you can. You will know that the tank is completely full when the antifreeze starts backing up into your shower. You also need to get as much heat as you can into the frozen holding tank.

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In some RV's there are furnace vents that run into the holding tank compartments if your RV has one of these setups you may need to crank up the furnace to a higher than normal temperature to melt some of the ice and allow the antifreeze to start working.

If you have a heat lamp available to you and you can "safely" place it near the grey water holding tank, it may provide enough heat to get the tank warm enough for the antifreeze to start doing its job and get things flowing again.

There are also Holding Tank Heater Blankets available that can attach to your holding tanks to warm them up and keep them from freezing.

I hope that this information has been helpful to you.

Do you have any suggestions or comments on this topic? You can add them to this page by clicking on the "Click Here To Post Comments" link located near the bottom of this page.

Happy RVing

RVing Al

P.S. Did You Know that you can build your own Web Page on Everything About RVing? Just Tell Us Why You Love RVing, Tell Us About Your Favorite Camping Or RVing Destination or Share a Funny RVing Story With Us.

Comments for How Do I Unfreeze My RV's Grey Water Tank?

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rock salt
by: Anonymous

I used 5# of rock salt down the toilet and hot water on a half full tank it took about 1/2 hour and it flowed right out.

Drive South
by: Anonymous

We had this happen when we were in British Columbia last month. We drove to southern Nevada and after a couple of days there the problem was solved.

Frozen holding tank
by: Kicknbak

Since we use our RVs all year round, I have always kept a few of those clamp on incandescent work lights with reflector hood handy. Frozen tank? Open the valve (if possible) Strap it under the tank with a bungee and wait. Low wattage lamp if there's no gap, other wise go up to 100w if there's a gap between the lamp and the tank. These lamps also come in handy if you're camping in freezing weather strategically placed near your waterworks just to prevent freezing... and don't forget to let your faucets drip at such times if too involved to winterize.

use salt
by: Anonymous

When my trailer froze up I thawed the valves with a hair dryer then i dumped 2 boxes of table salt down the standing water in the sink let sit and 3 hrs later the tank drained.

Easy Cheap way to unthaw tanks and valves.
by: North Dakota Vet

I'm currently in North Dakota living in my 28rls Heartland North Trail 32 foot trailer with my wife and 2 cats. It has a ABS covered and heated underbelly so I wasn't worried about the tanks being frozen.

It's roughly 6 to -11 degrees outside at night and I recently had problems with the waste gate valves freezing shut in our trailer. We had full tanks, and my wife and I needed to drain them. I figured out a quick 20-30 minute fix to thaw the valves and let us dump successfully.

What you need to accomplish our method is cheap and effective, and won't have you under your trailer with a hair dryer. This is a temporary fix, and should never be left in place.

What you will need: 1 small cardboard box, 10-15 feet of aluminum dryer vent, usually around 10-15 dollars from any hardware store, a knife or box cutter, phillips screw driver.

Close the bottom of the box so you aren't heating the ground under your valves. Form the top of the box so that there is a minimum amount of air escaping around the valve surfaces. Some ventilation I think is necessary so you aren't pumping poisonous gases back into your trailer or RV, so it's okay if it doesn't form around the valves perfectly.

Cut a hole the same size around as the aluminum dryer vent you will be using. I used 4" vent ducting. it doesn't matter what side you cut the hole. I used the same side as the furnace vent, since that will be where you are getting your heat. insert the dryer vent into the hole you cut in the cardboard box, stretch to reach your furnace exhaust vent. Be sure not to cover the inlet to the furnace.

Undo one of the screws on your inlet outlet vents for your furnace. using the same screw, put a small hole near one of the wires in the dryer vents on the other end of the vent. return the screw into the furnace vent so that the screw head "grabs" the wire of the dryer vent opening. Turn your heater up inside so that the furnace runs constantly for at least 30 minutes.

Do not leave this attached permanently! I brewed a pot of coffee, had half a cup and then tried my valves and they were UN-thawed for a successful dump. Hope this helps if you happen to be in an arctic climate. I'm not responsible for any damage you might cause your own trailer. maintain supervision while this process is taking place.

Black tanks
by: Anonymous

So how would I defrost a frozen black tank. Im sure heating it up would help but what about the rv antifreeze. Not sure if full or not BUT knowing its working by black water backing up the toilet would definately be an issue. What would be the best way Thanks

Gray tank is full
by: Dusty

Our grey tank hangs down under the 40' 5th wheel. You can see it under the coach. We didn't think we had an issue until the bath tube has about 2 inches of water in it and it won't drain. We got under the coach and put some heat tape on both tanks but now it is still frozen. Pushing on the tank under neath kind of tells me the tank is full, or close to it. So if we dump a lot of RV antifreeze down all the drains like in the bath room I wonder if that would take care of this issue. The tube drain goes into the same drain as the kitchen sink. So I wonder if we just dumped a lot of RV antifreeze down the bathroom sink if that wold work? We also have heat tape on all the lines too with insulation so if and when it thaws out it won't happen again. Any suggestions? Thank you folks so much.


How To Fix An RV Or Motorhome Frozen Grey Water Tank.
by: Anonymous

There is a simple way to get the tank warmed up and melting right away using the rv's furnace. If you have any tape. Tape up all your vents coming from the furnace with the exception of the vent closest to the drain in the bathroom. Use either a clean rv sewer hose or in my case I used 44 Oz.Pepsi cups taped togeter from the gas station Tape them together from the vent to the drain in the shower or tub. Wahlah Fixed in minutes. You can also run water on top of the tank outside to help expedite the process.In addition use your hot water heater with slow running water. You can use the stove to warm water as well. Works for sure. Mine was completely full and frozen. Took like 30 minutes.

excellent advice, worked well for me!
by: Tony

This year we left our RV trailer at a campground in the mountains, to come over at weekends for skiing etc. Due to the very low temperature in the area last week and (possibly) power issues, we found our camper very cold, pretty much frozen, and worst of all - grey water dump valve was frozen.

Adding some hot water did not help, so I was scratching my head how to fix it.

The advice on this page helped - I added 3 gal RV anti-freeze with hot water as suggested on this page and used heater on the valve, and it fixed the problem.

Thanks to the guy who posted it!

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