Gray and Fresh Water Tanks for the Peter Buck March 30, 2013

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1 Gray and Fresh Water Tanks for the Peter Buck March 30, 2013 Coming to trailering from the boating environment we were taken aback by the puny size of our 2006 fresh water tank (5 gallons) and the total lack of a gray water tank. Our 22-foot custom Devlin power cruiser had 50 gallons of fresh water and the entire ocean for a gray water tank. We felt that to be able to dry camp we needed to find a way to add a larger fresh water tank and a decent sized gray water tank. Space inside the trailer is limited and we wanted to preserve this for our stuff, which meant that the tanks had to go outside, and the only place available that made sense was underneath. Outside means we can t go winter camping in sub-freezing weather, but life is about making compromises and we felt that having more fresh water and a gray water tank while preserving inside space but limiting winter camping was the right way to go. The t@b frame is 6 high at the axle, tapering to 5 close to the front of the trailer body. The spare tire hangs down about 7 from the underside of the trailer floor. This defines the basic size and shape of the space available to place tanks. The space is further constricted towards the front of the body as the two frames make their bend to eventually meet at the tongue. The brake cable down the center breaks this space in two, and at the front of the body there s electrical and propane lines in the way. One concern is the placement of the additional weight relative to tongue weight. Since it s vital to keep tongue weight positive, the tanks had to go in front of the axle. To keep the additional tongue weight to a minimum, the water volume needs to go as close to the axle as possible. The axle to hitch distance is about 9 feet. The center of the tanks is about 1.5 feet from the axle. This gives a mechanical advantage of about 1/6. A full tank weighs about 83 lbs. Assuming a worst case scenario where the water tank had been refilled but the waste tank had not yet been drained, the combined weight of 166 lbs., let s call it 180 lbs. including the tank frame. This adds a maximum of 30 lbs. to the tongue weight, or 15 lbs. under normal circumstances. Judicious placement of personal items inside the trailer can reduce this if desired. Initially I planned to design custom tanks that would solve all of these constraints.

2 This example is tapered to exactly fit the frame taper and its rear out-board corner is an inch lower to ensure complete drainage of the tank. This tank would hold 12 gallons. The volume is greater towards the rear. Unfortunately this tank is too expensive to have custom made by rotomolding. I looked into fabricating it from sheet polyethylene using a new polyethylene glue from Tap Plastics but it seemed like too much work and the glue is not approved for contact with drinking water. Eventually I settled on two standard sized roto-molded polyethylene tanks from Custom Rotomolding (

3 This is their W33 tank, 6 high by 31 long by 15.5 wide. I had them spin on female threaded fittings, ¾ for inlet and outlet, ½ for vent. This is the gray water tank, which is placed on the driver s side of the trailer. The fresh water tank can be a mirror image (to keep the outlet outboard and away from the brake cable) or the outlet can be left off and a dip tube can be installed using a bulkhead tube fitting. When I received the tanks I installed 6 marine deck plates in the tops for access inside the tanks, both to be able to install the dip tube in the fresh water tank and to be able to clean them periodically. This is the completed fresh water tank, showing at the front of the tank from left to right in the photo the vent, dip tube outlet, and inlet as well as the deck plate on top. The dip tube was an attempt to minimize the distance from the water pump to the tank. The other option was to put the outlet on the rear lower outboard corner of the tank and run a hose forward along the trailer frame. Either probably works. The dip tube inside the tank is 3/8 polyethylene tube with a brass pipe nipple on the end to keep it weighted down since the tubing is stiff.

4 This photo was taken by lowering the camera through the deck plate opening. The tanks are attached to the underside of the trailer with a framework made from 1/8 and 1/16 x 1.5 aluminum angle stock. At the rear of the tanks just in front of the axle I attached a piece of 1/8 angle across the bottom of the trailer from frame to frame. The tank framework is hung from this with 4 1/8 x 3 x 7 aluminum straps. The front of the tank frame is attached to the trailer frame members

5 with ¼ stainless bolts. This photo shows the rear mount attached to the trailer bottom, two of the four 3 straps, the waste tank in the frame, and the fresh water tank ready to install. The front of the frame can be lowered and the tanks removed for service.

6 This shows the completed installation. I had to reroute the propane plumbing including replacing the rusted ¾ iron pipe with a shorter brass nipple and extending the propane line to the furnace since routing it along the trailer frame instead of directly across the trailer bottom required a longer length of tubing. Fresh water inlet and sink drain are plumbed directly through the floor into the cabinet under the sink. The ¾ nipples the go through the floor are caulked in place with silicon bathroom caulk.

7 Fresh water tank fill and vent lines are led to a fill fixture mounted inside the propane/battery box such that the battery can still be removed without detaching any of the plumbing. The waste tank vent is also routed here.

8 This shows the inside of the sink cabinet. The water inlet is to the rear of the two propane lines, the sink drain at the front.