Ask Dave: How do I drain the old DEF from RV’s tank and dispose of it?

Dear Dave,
What do you recommend to remove the DEF from the tank? Any recommendations? My RV has been sitting for quite some time (3 years) with the occasional short trip. I would like to remove what is in the tank, as I always keep the tank full, and then properly dispose of it. I am glad I saw your article in keeping the tank at low levels. —Richard, 2017 Thor 35SD

Dear Richard,
Since writing the article about the shelf life of diesel exhaust fluid (DEF) I have gotten several questions about proper disposal of the old DEF fluid. I tried to get an answer from the DEF manufacturers, CDC, or any “certified” organization. The only response I have received is, “It needs to be properly disposed of.” That was the question, so it’s not an answer.

Get the DEF out of the tank

But first, you need to get the DEF out of the tank of your diesel pusher. Since there is no drain plug, you will need to find a way to siphon it out from the fill neck at the cap. I have done this a few times on a Chevy 3500 as one technician filled it with diesel fuel and another put in two gallons of windshield washer fluid! Good help is hard to find. In both cases, I used a manual siphon, which was a hand pump with long rubber tube. It was soft enough to make the few twists and turns required to get to the bottom.

To siphon DEF out of tank

This is the type we used, as we could get the pump into the tank and could add more hose if needed. It also allowed me to pump as much as needed to fill the 2.5 gallon jug of the empty DEF container we had waiting to recycle. Luckily, we only had about 2-3 gallons to pump out as it was not filled and the container only holds about 4 gallons. Yours will probably be much larger. Most Freightliner chassis hold 25 gallons, so you will need more containers or something larger.

It is not recommended to use metal, as the urea can corrode metal. However, if you are getting rid of it quickly, it should not be a concern. You might be able to get a 30-gallon drum from a local lubrication supplier or agricultural implement dealer. I don’t think you need to get all of it out, maybe just 2/3. The new DEF will bring the concentration up enough to be good. However, if you are going to all the work of getting a pump and container, might as well get it all.

There are several other types of siphons and pumps available at auto parts stores or Amazon such as this one.

How to dispose of old DEF

So what do we do with it once it’s out? DEF is 65% distilled water and 35% (approximately) urea. Urea is used in fertilizer, so you will see a whirlwind of forums recommending to dilute it in more water and spray it on your lawn. This is not recommended by the DEF manufacturers, CDC, chassis manufacturers, or anyone other than the “chats” that provide no documentation or research pertaining to environmental regulations. Even with fertilizer applications, there are certifications required for agricultural and commercial application which urea falls under. There are also regulations pertaining to ground water and watershed issues, as well as local regulations.

I contacted our local Petroblend distributor who is a major supplier of oils and DEF for commercial trucking and agricultural applications. They also did not recommend just dumping it, but rather taking it to a Hazardous Waste Materials Recycling Center. So I called the Landfill Of North Iowa, since they have an outstanding Hazardous Materials department. They stated that they do accept DEF, as it falls under the Fertilizer/Herbicides/Pesticides category for agricultural applications. The fee is $10, as the 20+ gallons would be considered Agricultural. They stated that a smaller container of 2.5 gallons would be considered residential. It would again fall under fertilizer, or possibly engine fluids, and be no charge.

No “authorized” statements for other disposal options

As of this time, there have been no “authorized” statements pertaining to any other disposal options. However, I would imagine there will be some recycle centers that may eventually offer the service such as those that will take used engine oil, brake fluid and other liquids.

Dave Solberg is a leading expert in the RV industry and the author of the “RV Handbook.”

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