Holding Tank Systems
Our holding tanks are manufactured using smooth, high density polyethylene which has an excellent weight to strength ratio and stays clean.
Baffles are incorporated at 300mm spaces. These baffles are welded all round, using the latest hot gas extrusion welding technology. Additionally they are lock jointed to the tank top. It is here where moving contents imposes maximum strain. This movement is reduced to a minimum by the baffles. With 1 cubic foot weighing 62 pounds, dynamic forces inside a tank are considerable.
Tanks must also withstand pressure created by inadvertent over filling. A vent filled to only 1 metre above the tank will exert an upward force, into the tank top, of .75 Kg on each square cm, over the whole area.
Our rigid tanks are supplied with inspection hatch and connections fitted, all pressure tested, For small boats there is an increased demand for flexible holding tanks, they can be easily installed in small spaces difficult to access. A rigid tank should be preferred if the necessary accommodation is available.
Boat owners who complain of smelly holding tank systems have experienced old and poorly maintained systems, or the system could be badly installed and/or using incorrectly specified equipment. Standards call for an installed pressure test. Our tanks are pressure tested allowing for a vent rising 2m (6'6") above the tank. Vents should not rise above this height and ideally breath through the hull side below the gunwale. The standard rigid tanks offered are supplied with the fittings installed in the top surfaces to customer's specification. Alternatively, with a slight lead-time, special tanks are made to order. Manufactured in clean smooth and tough polypropylene.
A 38mm breather must be accommodated. This can be made up by a multiple of smaller breathers, equaling the cross sectional areas of 38mm as long as none of the breather pipes are below 16mm internal diameter. Lee Sanitation can also offer an automatically opening inlet vent, which can be used in conjunction with a permanently open vent of not less than 16mm ID.
All these systems conform to the various applicable national and international standards both existing and proposed. We strongly recommend, wherever possible, a full permanently opened 38mm ID vent as the preferred option. This allows both the discharge of displaced air and the free flow of air in, to retain the effluent in an aerobic condition. Tanks with small breathers will almost certainly turn anaerobic. It is in this latter condition, created by the absence of oxygen, that malodours occur.
Rotationally moulded, more economic tanks are now available in limited sizes. They have the similiar exacting standards as the other tanks we sell, only slightly cheaper.