Where are the tanks?

[kb0zke]

Many travel trailers have the fresh, black, and grey tanks mounted in the belly of the trailer. To service them the coroplast belly skin needs to be removed, which is accomplished by simply removing several large self-tapping bolts. Airstreams, though, have an aluminum belly skin, held in place by rivets. NOT and easy remove and replace proposition. So, where ARE the tanks in an Airstream? We're specifically looking at 2015-2017 or so 30' and longer rear queen bed trailers, if that makes a difference.

[richard5933]

The tanks are between the frame rails hidden by the belly pan. Access is by pulling the belly pan. But, I haven't heard of many tanks needing replacement, especially for trailers built within the past few decades.

Servicing the tanks is also possible by cutting an access hatch, which is what I did when I replaced the dump valves on my 1994 trailer, and that appears to be the only attention they've needed since 1994.

[kb0zke]

Thanks. One of the issues that has been discussed on the Grand Design forum is tanks that are not well supported. One person actually had a tank fall out (!) because the coroplast isn't strong enough to hold it. I suspect that, even if a tank somehow got loose, the aluminum belly skin would keep if from going off by itself.

[AlbertF]

Airstream uses galvanized sheet metal boxes to hold the plastic tanks in place. There is a layer of expanded polystyrene insulation in there as well. The furnace ductwork extends to the steel boxes to blow warm air in while the furnace is running.

On larger trailers, the tank assemblies are hidden above the aluminum belly skin. On smaller trailers like our 22FB, the galvanized boxes are visible below.

The water tank is typically just ahead of the front axle. This means that a full tank of water has only a nominal effect on tongue weight - something in the range of 50 to 100 lbs in most cases, I'd guess. A full water tank also helps lower the trailer's centre of gravity a bit more, so it's not a problem for towing.

The black tank will always be right below the toilet. There should never be any piping; the toilet flange is connected directly to the black tank.

The grey tank will normally be in the rear.

There have been cases of full water tanks coming loose. With our old 1975 Airstream, the boxes were held in with angle steel frames bolted to the frame. On newer trailers, straps and bolts are used. Some people have reinforced them. This is likely to be more of an issue with larger tanks. The water tank on our 22 is only 20 US gallons - 166 lbs.

I'd agree that tank replacements are infrequent. I had the original waste tanks of our old trailer out when it was 36 years old. The framework was rusting away and the galvanized boxes had holes too. I had a mechanical shop make up new boxes, and welded up a new frame. But the original plastic tanks were in excellent condition.

[kb0zke]

Thanks, Albert. Good to know. As I said, we're looking for a trailer a bit newer than your old one, probably not as new as your current one.


Your description of exactly where each tank is located will really help me visualize things. I generally prefer to travel with the fresh water tank at less than full, and the grey and black about half full. That way the sloshing of travel keeps things all shook up, so that when we arrive I can dump and know that I'm actually dumping almost everything that was in the tank.


Yes, I do understand the weight issue involved. As I said, I "generally prefer" to travel as described, but I have no problem traveling with the black and grey tanks dumped first if necessary.

[kb0zke]

I went back and looked at some pictures of trailers like what we will be looking for. Looks like the toilet is just aft of the rear axle, so the black tank would be there. Would the grey tank, then, be aft of that, or would it be above and between the two axles?

[AlbertF]

Originally Posted by kb0zke

I went back and looked at some pictures of trailers like what we will be looking for. Looks like the toilet is just aft of the rear axle, so the black tank would be there. Would the grey tank, then, be aft of that, or would it be above and between the two axles?

I would not expect to see a grey tank between the axles.

We rarely stay in RV parks with full hookups, so we are typically driving some distance to a dump station. I think even a short drive of a half mile helps a lot to mix things up and break down toilet paper. We never use tank additives, and rarely even have odour. Of course, we don't have 115 degree heat where we live either.

[jeffmc306]

David, that’s interesting about the Grand Design tank dropping out.

Ronnie Dennis showed how he installs straps under the fresh water tank in the KYD video on their 30’ Globetrotter after installing a 3” lift. Fast forward to 15:35. The bottom of the tank is now almost flush with the axle.

I recently installed a set on our 27’ Globetrotter but since we don’t have the 3” lift, the tank sits lower. I bent the straps to fit the tank so the u-bolts could sit higher.

For what it’s worth!

[kb0zke]

The story about the tank falling out was posted on the Grand Design owners' forum a couple of weeks ago. It wasn't our trailer, and I don't remember there being any pictures. I also don't remember how old the trailer was. It does seem, from reading the comments, that some people believe trailers build during Covid weren't as good as those build before or after.


From looking at the "insides" of our trailer, I'm not overly impressed with how the tanks are mounted. We've toured several RV factories, including Airstream, and there is a BIG difference in how the work is done. Generally, the more expensive the whole lineup is the better the quality of the work.