Dual-bucket mash - 5L deadspace?

[Middo]

Since I don't have a boiler, I've been mashing my grains in a 15L stock pot and then pouring the mash into a dual-bucket setup - an outer bucket with a tap and one that fits inside with hundreds of 2mm holes drilled in the bottom. I get around 75% mash efficiency and it seems to work OK except for two things - I have to pour a hot, nearly full stockpot into the setup and I'm limited to 4kg of grist due to the size of the stockpot.

I've been thinking of using the dual-bucket setup as a mash tun, but due to the way the buckets fit inside one another I'm left with 5L deadspace between the bottom of the outer bucket and the bottom of the inner bucket, which means I'd have to add 5L to the total amount of mash liquor. Will this still work or will the extra liquor (that won't come into contact with the grist) be a problem? Has anyone else tried this or have a similar setup? or should I just fork out the extra cash and buy a boiler?!

[OldSpeckledBadger]

Having tried both stock-pots and dedicated boiler I think a dedicated boiler is a good idea regardless of mash tun construction. WRT to your MT, I assume you simply have a tap to draw the wort off. If you fit a pipe on the inside you should be able to get a syphon effect and reduce your dead space. Alternatively you could try simply tipping the MT.

[Scooby]

Why don't you buy a grain bag and suspend that in your bucket, wrap a few layers of camping mat round it, not forgetting the bottom and more importantly the lid them mash in there. if well insulated it will easily hold mash temp for 90mins.

I don't see a problem with your first idea except efficiency may suffer. You could insulate that as mentioned above and just use your pot to heat the mash water and boil.

[Middo]

Hmmm, I suppose I could place a dinner plate on the bottom of the main bucket so that it rests on the inside of the tap and prevents the grain bag from clogging it up. Seems a shame to bypass the straining bucket (as it's pretty much useless with all those holes in the bottom!) but I suppose it could still be used as a hopback after the boil?

With regards to the camping mats, does anyone know where these can be purchased cheaply? I've looked into it before and Mountain Warehouse charges around £10 each.

[Middo]

Good idea about displacement with marbles - that never occurred to me. I'll try trimming down the moldings first and see how much space is left, then go from there.

[WishboneBrewery]

Cheap camping mats are available from ebay, I used 2 camping mats to cover a 15L bucket, I think the same 2 mats would also cover 23/25L bucket.

[Middo]

Good idea about displacement with marbles - that never occurred to me. I'll try trimming down the moldings first and see how much space is left, then go from there.

This didn't turn out quite as well as I had hoped: yes, the buckets sit more closely together, however, they fit so snugly I can't separate them! The inner bucket seems to be jammed inside with a film of water between them causing a vacuum, making it even harder to separate them. Any ideas on how to get the inner bucket out or will I just have to cut it to pieces?!

[WishboneBrewery]

You could put the bottom in a hot bath, the outer bucket should expand first. In theory