Neil's Portable Heavy-Duty Soaking Tank

We needed a big soaking tank to use at the BA York Spring School. The design that I used was based on materials I had to hand rather than engineering considerations. Some 50 x 50 x 3mm angle irons and 19mm exterior plywood sheets were cut to size and assembled using steel bolts as corner pegs.

I have several different sized end panels, so for general day to day use, the tank is only 8ft x 2ft, but it can be made larger for use on courses, or for soaking very large pieces. A dimensioned technical drawing is available here as a PDF file.

If you reproduce the tank, please remember that huge amounts of water like this are potentially dangerous. The 8ft x 5ft version, which is 2ft deep, holds around 2.2 tons of water when full. Two tons of water can do serious damage when released suddenly or in an inappropriate place. The corner pegs MUST be at least 10mm steel bolts as there ae huge forces on them. The 50 x 50 x 3mm steel angles are the absolute minimum size, so if you intend making the tank any larger, you must use larger pieces of steel.

You must find a level surface to locate the tank on, and you must sweep it well to remove anything sharp and then cover it with old carpet or feed sacks or something else to prevent punctures. The surface must be strong enough to support a very large car or small van if the tank is to be filled up, something like a concrete garage base will be OK, but take care on a patio or other non load-bearing surface, and never put the tank on a wooden floor.

Make sure you position the tank so that it can be emptied into a suitable drain using a syphon - the bottom of the tank must be above the level of the drain or else you will have to bail it out by hand. The easiest way to empty the tank is to use cheap submersible pump. I use a Draper model that can empty two tons of water in 45 minutes.


The tank laid out ready to assemble. Each piece is made from 19mm external plywood with
a pair of 50 x 50 x 3mm mild steel angle irons bolted on for stiffening


Close up of a corner with 12mm hole


Assembling two sides


Aligning the fixing holes


The pegs for the corners are made from 10mm steel bolts with the ends ground to a point to ease assembly


Inserting one of the corner pegs


Corner peg in place


Corner assembly completed with a peg at top and bottom


Final side ready to be assembled


Completed assembly of the 8ft x 5ft (2.4m x 1.5m) version


Smaller version, 8ft x 2ft (2.4m x 0.6m)


Tarpaulin waterproof liner being prepared


Olivia and Kay using Kay's version of the tank