Using a hot water system expansion vessel as a beer tank

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lee smeaton

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This may not be as daft as it seems - hear me out.
Many domestic hot water systems have a pressurisation tank / expansion vessel in the system to maintain the hot water output pressure at high flow. In a home setup these may be 10-20 litres, however I deal with ones in hotels and office blocks that are much larger.
for those that don't know, these look a bit like an immersion heater - the key difference is that they contain a flexible bladder, sometimes neoprene, sometimes rubber, sometimes something a bit more exotic.
The way they work is that the bladder is connected to the liquid line that you want to maintain the pressure of, The actual vessel remains dry with the bladder of liquid inside. The vessel has a small bicycle style valve into which gas (usually nitrogen) is charged - generally up to 3 or 4 bar.
In service the water pressure tries to fill the bladder but the gas pressure acts against the bladder- hey presto it helps to regulate the liquid line pressure.

I am thinking of using one for beer

I currently have a Cornelius type keg hooked up to a S30 c02 cylinder to supply beer to my tap. The downside to any C02 system is getting (and paying for) the gas.

My plan is to use a hot water system pressurisation / expansion vessel (bladder material would be key with regards to not effecting taste)

I would empty the gas charge out of the dry side of the vessel. I would then fill the bladder with beer with a conditioning dose of sugar. (as you filled the bladder with beer you would need to keep venting air pressure off the dry side and you might have to pump the beer in.

In theory the beer should create some c02 of its own and build pressure.

now, using a bicycle pump or stirrup pump you just pump up the dry side of the vessel - increasing the pressure in the wet side without introducing air into the beer

This should then give you a pressure keg that you can keep pressurised just using air - without spoiling the beer. In theory if you are running a multiple beer system you could rig a small air compressor via a reducing station to manage them all. In the picture below imagine the water is lovely beer.

main downside I can see at the moment is cleaning.

Happy to be shot down in flames but I think this might have legs.
expansion tank.jpg
 
I've made a small calorifier for my van from one of the 25L stainless ones. For that I cut out the end fitting just leaving the clamp ring, and made a new end plate from 3mm alloy plate.

Your idea sounds good but there would be a slight issue with cleaning in that you would probably have to take the end plate off to clean the bladder. This is only 6 bolts on my stainless one, but the threads are just rolled into the thin stainless so may not take multiple disassembly operations before you cross thread one.

You could just connect it to the top of a barrel and use the bladder with co2 on one side and compressed air on the other.....bit like a big balloon you can squeeze. Then you probably wouldn't have to clean it as it should just have CO2 in it.

Nice idea...have fun.

I just thought - you really just need a thick rubber balloon attached to a schrader valve inside the keg - then you could use air to inflate it and the two gasses don't mix.
 
I'm in the process of buying some scondhand ecofass kegs as my cornies are all in use. They have sankey S fittings.
30l Plastic keg with recyclable bladders. https://www.ecofass.com/en/ they can be charged with air, or co2 and will not need sanitising, unless attempting to re-use the bags, not sure if that is practicable though,,, will update once I get them!
 
Just my 2pence worth, but an expansion vessel is exactly that, it takes up the expansion and warm pressurised water that otherwise has nowhere else to go.
These vessels have no effect on water pressure or regulation of that, that is taken care of by a pressure reducing valve.
I routinely deal with these on heating and hot water systems that have failed and the air side has filled with water, in your case, that would be beer l, which I could see having a detrimental impact on the final product.
 

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