Plastic Keg to MLT conversion - need suggestions

So I managed to get a plastic keg because it has a huge crack in the bottom. I'd like to convert it to an MLT. The crack isn't an issue because it's the part of the bottom I'd just cut out for an opening. The problem I have is that the opening at the top isn't the same size as a standard keg. The inside of the opening is the standard 2'', but the outside of the plastic is 2.5''. It also doesn't look like a tri clover clamp will work on it. I'm looking for any suggestions people might have of being able to hook up some sort of elbow to a ball-valve coming from the opening. Here are some pictures.

Any chance of getting a cheap/free coupler from the same place you got the keg? If so you could probably modify for your use.

doubtful, but possibly. I'd need a stem assembly too though. Would I be able to take it apart, removing just the stem so that the coupler can still attach, but I can drain straight from the bottom?

I would imagine you could adapt the coupler but honestly without seeing it hard to say for sure. If you can get a look at one you could probably decide. I especially wouldn't pay for one before I knew it could be modified.


As long as you have a false bottom installed I can't think of a reason why you wouldn't be able to drain directly below it, there would be no loss of wort from mash/lauter tun dead space!

you could cut the bottom as planned, then get a tap and die set large enough to put threads inside your top opening. thread on a ball valve or whatever you plan to use. Insert false bottom and away you go

Well the top opening already has threads for the spear assembly. I think I'm going to see if they have an extra spear assembly. Looks like I could remove the spear itself leaving the top portion. Then I could just plug up the gas port on a standard sankey coupler.

The other option that's been mentioned to me is looking for some sort of rubber boot that I could hose clamp to the opening and an elbow then hook the valve to the elbow.

if it is already threaded, then get a nipple and a reducer and attach a valve. Or get a 2" plug and install. then pop a hole in the side if that is what you want to do.

oops, my mistake. I misunderstood how these things work. I guess it's not threaded.

With a little creativity and a few basic plumbing parts you can create a drain without the use of a tri-clamp.

https://www.homebrewtalk.com/f51/start-another-herms-192608/

How did you create a seal between the copper pipe and the side? Some sort of epoxy?

Try to plumb it...or take a piece of scrap from the cut out bottom of the keg and Plastic weld the top opening shut with a disc of the scrap plastic, and perhaps some thin plastic strips sorta like welding rods...I have never done it but hdpe can be melted and welded AFAIK and it soesn't need to hold much if any pressure...try a propane torch but go easy...then put a bulkhead in the side of the keg...

Not really worth spending a bunch of money on fittings, but a fernco or a shielded coupling couls also wrap the flange if you wanted to try bottom drain.

LoneWolfPR said:

How did you create a seal between the copper pipe and the side? Some sort of epoxy?

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The side of what? I'm not sure what you're asking, but there was no epoxy or glue used. It's entirely mechanical connections and silicone o-rings/washers.

I made this for my upsidedown HLT, i like the disassembly aspect of it but i don't know the best way to attach it to your keg.

https://www.homebrewtalk.com/f51/bottom-drain-questions-265766/index2.html#post3220354

JuanMoore said:

The side of what? I'm not sure what you're asking, but there was no epoxy or glue used. It's entirely mechanical connections and silicone o-rings/washers.

Click to expand...

The pipe that goes up through the opening. How is that sealed? Does it screw into the opening?

LoneWolfPR said:

The pipe that goes up through the opening. How is that sealed? Does it screw into the opening?

Click to expand...

There's a male 1/2" copper fitting inside the keg that screws into the brass elbow on the outside. There's a SS washer on each side that compresses a silicone gasket on one side and a silicone o-ring on the other. It's all broken down and explained in detail (with pictures) in the thread I linked above. Did you not read the thread?

Ah, I see. Like I ******* I didn't read far enough ahead.

LoneWolfPR said:

Ah, I see. Like I ******* I didn't read far enough ahead.

Click to expand...

No problem. I just wasn't sure how to describe it any better than I had in that thread.

Ok. looking at it I think I'll probably wind up using your method mostly. the only difference I see is that instead of the brass elbow I think I'm just going to put a female brass fitting coming with barb for PEX. That way I can have flexible high temp pipe coming out. Is there any reason not to use PEX?

LoneWolfPR said:

Ok. looking at it I think I'll probably wind up using your method mostly. the only difference I see is that instead of the brass elbow I think I'm just going to put a female brass fitting coming with barb for PEX. That way I can have flexible high temp pipe coming out. Is there any reason not to use PEX?

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I went with copper since my HLT is direct fired. As long as you're not direct firing, I don't see why PEX wouldn't work.

Nope, no direct firing (Plastic keg and all)

I bet you could use an appropriately sized stopper. Drill a 5/8" hole in a stopper, insert a 1/2" NPT stainless nipple and pound it into the opening from the inside.

Can a rubber stopper handle temps up to 175?

Nevermind, EPDM rubber stoppers have a max temp of 150 deg. C. So that could work too.

The alternative is to measure it and actually tap new NPT threads in. If I'm guessing, probably 1.5" NPT would be close. The problem is the insane cost of a tap that big.

Bobby_M said:

The alternative is to measure it and actually tap new NPT threads in. If I'm guessing, probably 1.5" NPT would be close. The problem is the insane cost of a tap that big.

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Since you are only threading plastic, you could make a "ghetto" tap out of a black pipe threaded fitting, basicly make 6 or 8 longitudinal cuts w/ a hacksaw in the threads and it will function as a tap and cut threads in the plastic.

For that matter, tapered pipe thread might just "make its way" with that soft plastic and thread in with a large pipe wrench, like you would with a tap, 1/2 turn in, 1/4 turn out, repeat. (lil heat to soften the plastic might not hurt either)

I talked to the folks at the brewery. They've got some extra parts and are going to give me the top of the spear assembly. It's actually specially designed for these kegs and screws into the opening.

I got the top part of the spear/valve assembly today. I realized I could connect a ball valve via a fitting to my low profile sankey tavern head and voila! ready made drain. I'll probably wind up doing something like that.