Fixing 2 x bilge pumps inside plastic 25 gallon loft tank

[bowlingo]

Hi all,

I am working on a project and need to screw 2 x large bilge pumps to the bottom of a 25 gallon plastic loft tank...here is the tank

http://www.bhl.co.uk/product/POLYTANK_PT2000_27X20X20_25GAL_RECT_INS

At the moment I have stuck a piece of plywood to the bottom of the tank using gorilla glue and screwed the bilge pumps onto it using 12mm long fat wood screws.... but its only a question of time before the plywood comes apart and the bilge pumps fall over.

I am thinking of say a 15 - 20mm plastic sheet of which I will glue onto the bottom of the tank using a 2 part adhesive mix..

Ive just bought some of this

http://www.bondloc.co.uk/#/b2025/4549013881

The plastic that I stick to the bottom of the tank and screw the pumps to would have to be of such a density that when I screw into it it would grip the screws tightly like the ply im currently using does.

Does anyone have any ideas on a better way or where to get a sheet of suitable plastic thats 500mm x 400mm x 20mm ?

Thanks
Alex

 

[RedHerring2]

Countersink the holes in the bottom of the plastic sheet and use machine screws and nuts to fix your pumps, something like these:
http://www.thesitebox.com/screws/machine-screws/stainless-steel-slotted-countersunk.aspx

You could also use stainless steel screws and nuts.

Or even use nuts and bolts. Countersink the holes in the bottom of the plastic sheet, then shape the countersink, say with a hot bolt head, to create a shaped countersink that will 'capture' the bolt head.

 

[bowlingo]

Very good idea...

The trouble is the plastic sheet thats glued to the bottom of the tank can never come off again...melting the hex nuts into the bottom of the sheet might work though so if the pumps ever need replacing or cleaning I could screw back down into them.

It would be a lot better if I could simply screw the pumps directly into the plastic sheet but im not sure how well plastic would grip in relation to say plywood (Already using a plywood sheet)

Thanks

 

[TicklyT]

Set Tee nuts:-

into the bottom of your plastic insert before fixing it down, and fix your pumps to them with machine screws from the top.

Or, using an alternative form of tank, such as:-

Chosen so two tanks the same size 'nest' together neatly,

Fix your pumps with bolts straight through bottom of one tank, and drop the entire assembly into another tank.

Add a few 'drain holes' through the inner tank to stop it floating as it empties.

It sounds like you are making life over-complicated by trying to avoid piercing the tank. Most plumbers achieve watertight seals around fittings (tank connectors etc.) bolted straight through the sides and bases of water tanks without any problems, just by fitting the right type of washer on the right side of the fitting when assembling them.

 

[big-all]

why not have the big tank feeding a smaller metal tank as a sump as the weight and vibration will probably cause leaks of failure