I installed two tanks under the bed of the trailer. One tank is about ten gallons, for fresh water. The other tank is about 13 gallons, and is for for grey water. My meaning of grey water is the water used for dish washing, rinsing food, and washing hands or brushing teeth. There is considerable space under the trailer bed, between floor and axle. If the road conditions are such that I do not strike the axle, I will not hit the tanks, either. Theoretically. I guess I could still bash the plumbing near the rear of the trailer, especially when backing into a campsite.

A grey water tank is useful for us, because we have stayed at some campsites where grey water is not supposed to be simply tossed on the ground. While these sites have a special facility connected with the toilet building, it is awkward to carry a basinful of water across a campground to dump properly.

In searching the internet I found a supplier of ready made black plastic tanks for grey water. The tank I chose has a stepped bottom, so part of it will fit very nicely between axle and floor. The tank also has a flange on its upper edge for mounting it. I will use carriage bolts long enough to reach all the way through the floor insulation and the floor material. The linoleum will then be defaced with a group of rounded carriage bolt heads, but they will be hidden most of the time by the bedding.

I should have ordered a mounting flange or socket attached to the greywater tank when I ordered it, or at least ordered the darn flange when I ordered the tank. It would have only cost a dollar more. I didn't. uffda! Shipping for this little item by itself was six dollars if I ordered it after the fact. Darn! I was not gonna do it! I happened to have some black plastic pipe of the right size in my basement collection of odd bits and pieces, so I decided to make my own flange. This is a thermoplastic. That means if you heat it up, you can shape it to your desires. I made a wooden form for the flange. I put a short piece of the pipe in the mold and then heated the pipe up with a heating element that is otherwise used for softening old paint for scraping. As I heated the plastic, I tested its plasticity with a bit of wood, to see how easily it would deform. When I was satisfied with the heat, I flattened out a flange on the exposed end of the pipe, and weighted down a board to hold the flange shape until the plastic cooled. I cut a hole in the tank where I wanted the outlet to be, and used the appropriate pipe cement to fasten the pipe flange over the hole. It looks just like it was done the regular way.

I also made a flat piece of plastic to be glued to the tank where I wanted the vent line. Again, I cut a piece of plastic pipe, slit it and then flattened it with the help of some heat, a board and a clamp. When the plastic was cooled and rigid, I cut it to the shape I thought I wanted, and glued it to the tank. When the glue was cured, I drilled and tapped a hole for the compression fitting for the vent line.

The fresh water tank was ordered from another company. It is of white poly and has two threaded connections on it, per my specifications. One connection is at the top of the tank, and the other connection is at the bottom, on opposite ends. It is standard pipe thread, and there is a whole host of fittings available locally for my choosing.

I made a steel framework to fasten the tank to the underside of the trailer, using ordinary flat bar, about 1/8" thick, and about 1 1/4" wide. When I fastened the tank to the underside of the trailer, I shimmed the rear of the tank downwards, away from the trailer, about an inch. The forward end of the tank is in contact with the underside of the trailer. My thinking was that if the trailer is leveled, I wanted the rear end of the tank to be lower than the front, to be able to get more usable tank volume. The tank has a flat bottom, and the fitting is mounted at the lower edge of the tank end. No water will come out of the lowest inch or so, of the tank. If the tank is tilted somewhat, I will be able to get a bit more water out.

I squirted some foam into the space between the underside of the trailer and the top of the freshwater tank, to try to keep water and debris from accumulating in this space, and also to try to keep the tank from vibrating and rattling in the frame.

Some details of the plumbing, showing the greywater plumbing on the left, and the freshwater plumbing on the right. The vent lines are 1/2" flexible poly tubing. In my opinion, there is a state of anarchy existing in the plumbing trade. The tubing is 1/2". The compression fittings for it are 5/8". One system uses outside dimensions of the tubing, the other system uses the inside dimensions of the tubing. I just bring a sample of the tubing with me to the hardware store, and get whatever will fit. Note the flex tubing from the hand pump is in a loop, so it will not kink, and is attached with a "barb" fitting. I do not recall the size, but the barb is screwed into a 1/2" plumbing tee.

The funnel is from the local hardware store. I heated the end and screwed it into a plastic hose fitting female/male adapter which screws into the female hose fitting shown in the above picture. When pouring water into the funnel, there is a small amount of leakage from this fitting, but it accumulates in the well shown above. I clean it up with a sponge. When the tank is full, the water overflows into this well... and I clean it up with a sponge. The brown stain in the upper picture is some discolored epoxy around the female hose fitting, in the well. I have another funnel for dumping dishwater into the grey water tank. The well for this is similar, except there is no threaded hose fitting. The end of the funnel is plain, and shrunk down to fit snugly into the drain pipe. The funnels can not be mistakenly interchanged, so that the grey water funnel is accidentally used for filling the fresh water tank. The funnels are also kept in separate resealable plastic freezer bags. I made a "key" for removing the covers of the respective tank wells. The lids are two different sizes also, so they won't be accidentally interchanged. The wells are made from standard plastic pipe caps and plugs, modified for my needs.

This is a PVC pipe cap, slightly modified. I drilled and filed as needed, to get a hole in the bottom of the cap. The fitting is sealed in the hole with epoxy putty. On the side of the cap is a street ell, which is an elbow with female threads on one side and male threads on the other. In this case the size is 1/2". I drilled and threaded the side of the cap to take the ell. I did a test fit of the ell, to see how far into the cap it went, and filed some notches into the end of the ell, to match the threads inside the cap. When the plug is screwed into the cap, it goes in far enough to block the end of the ell. This minimizes the amount of water that can slosh into the cap, back through the vent line, when the trailer is moving. Pipe threads are tapered, and I had the pipe plug reversed to present a flat surface on the floor of the galley. This meant a considerable amount of filing, to allow the pipe plug to screw into the cap, reversed. The threads are a loose enough fit to allow air to seep back into the tank whenever water is drawn off with the hand pump.

I first tried screwing the various threaded plastic pipe fitting together dry, but there would be weeping leaks, so I took things apart and then used joint sealing compound to make sure the joints did not leak. Not all sealing compounds are chemically the same. Make sure you use something compatible with plastic. I ordered my plastic pipe fittings online. This was good for me, because I do not speak plumber's language, and my local shops do not carry  much in the way of what I needed. The website I used was  http://www.plumbingsupply.com/pvc.html  and I like this site. It has plenty of explanatory material for the layman like me to be able to order what I needed. There are plenty of good illustrations, plus many hot tips and helpful hints - like the one about compatible thread sealing compound. I have nothing to gain from posting this link, it is just a good and useful site. Delivery was prompt and reasonable, too.

There are two valves for the fresh water tank. One valve is for filling the tank. It is a ball valve with a red handle on it. A quarter turn opens the valve completely. When the tank is filled, I shut the valve. I need to reach under the bed of the trailer to do this, but it is not a long reach, so is no problem. The other valve is used for draining the tank. I also use this valve if I want to fill a kettle or saucepan or other vessel, as it is faster and easier than using the hand pump inside the galley. I keep a pipe plug in the outlet of this valve when it is not in use. If for some odd reason the valve is not completely shut, the plug will keep the tank from draining. The plug also keeps the outlet of the valve clean. At first, this valve was also under the bed of the trailer, but it was an aggravation for my wife to reach for this valve — and she was right in wanting the valve moved to a more convenient position.

The 2 inch slide valve on the left has a threaded pipe plug in it. When I want to drain the grey water tank, I remove the plug and attach an 8 foot length of shop vac hose which has a male thread fitting on it, and then pull open the slide valve. The red-handled valve on the right is a 1/2 inch PVC ball valve. I can drain the tank with this valve, or use it for filling pots and kettles. The valve has a threaded pipe plug in it, to keep it clean.

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