Gray Tank?

[Bordolover]

I picked up a 1970 27' Overlander last year for northern California work. Currently use it for about 5 months a year in the summer and fall. My understanding is that there is no gray tank in the 1970 Overlander. However, I have noticed a tank under the double bed. While sealing the wheel wells with rubberized spray paint I noticed a vent tube coming down from the top of the streetside wheel well. Under the bed this vent then goes into the floor along with another pipe that has a cutoff valve similar to the black tank dump valve and the existing gray water shutoff valve located in the rear of the trailer. Underneath the trailer it appears that there is a tank located streetside under the bed area with a 3 inch tube that runs across the trailer through this tank.

I was looking to find the cause of the road dust and debris that seems to accumulate in the rear bath during towing and figured this vent in the wheel well might be the culprit. However, the vent pipe goes into the floor through an opening that is cut into the plywood flooring. I plan to filter these openings with some sort of material and see if that is the entry point for the dust.

But, does anyone think that a gray tank was added and I was completely unaware of its existence? Is the shutoff valve under the bed to allow flow into the tank and the 3 inch tube that runs across the trailer and opens right behind the curbside tires for the the draining of this tank?

How are the gray tank modifications made for a 1970 27' Overlander? If I do have a gray tank it will make dry camping quite a bit more doable.

[57Vintage]

I don't believe grey water tanks were standard until the mid 70's. I assume your tank under the bed was added by a prior owner if its for grey water. Any chance its for fresh water? Is there a line with a pump coming off the lower side of the tank? How its plumbed or its intended use is difficult to sort out without photos.

The drain from the tank will normally end in a 3" line with a shutoff valve if its grey or black water tank drainage. Your vent in the wheel well; does it appear to go to the top of your tank? Vent lines normally go out through the roof to keep odors away from you.