Simple Self-filter Mash Tun for All-grain Beer

We all like beer :-) and home brewed all-grain beer is even better. You get to have control over your ingredients, try out new recipes, and share great beer with your friends. Homebrewing is getting more and more popular.

When I started homebrewing I found that filtering the spent grains and the spent hops out of the brew was difficult and messy - I initially used a muslin! - and so a trawl of the internet started, looking for better ways of doing the filtration.

I came across this suggestion of using the steel braid outer from flexible plumbing pipe, and have been using this method for several years.

The stainless braid has thousands of tiny holes, so it acts like a filter. When attached to the inside of a tap, you just open the tap and out comes your filtered wort. It works well for filtering out both the spent grains and spent hops too. Having the filter built into the equipment like this saves SO MUCH time and mess it's unreal. Don't do all grain brewing without a self-filtering system.

I'd meant to do an Instructable showing how to make this cheap self-filtering brew vessel ages ago, but hadn't got around to it. Recently a part broke so I had to do a minor rebuild, so I thought it would be a great opportunity to take some photos and do that Instructable.

(Due Credit should of course go to whoever it was, on some Brewing forum somewhere, that suggested the idea of using the stainless braid in the first place)

Step 1: Tools and Materials

Simple Self-filter Mash Tun for All-grain Beer
Simple Self-filter Mash Tun for All-grain Beer
Simple Self-filter Mash Tun for All-grain Beer
Simple Self-filter Mash Tun for All-grain Beer

1) a large catering size stock pot

I got mine from eBay a number of years ago. SIZE: mine is 33 litres, this means I can make a 25 litre batch of beer easily, yet when full of water I can still carry it! MATERIAL: Do NOT get an aluminium one - beer is quite acidic and the aluminium ions will end up in your beer (not good).

2) Brass garden hose tap

Depending on where in the world you are I guess the type may vary. In the UK, these taps have a 1/2" BSP (British Standard Pipe) thread on the back, and the front has a 3/4" BSP connector for a hose pipe.

3) Tank connector. (this was the bit I was replacing, so I have a link to where I got them from: It's a 1/2" BSP threaded female, with a long tail of 3/4" threaded male, allowing for connection of the braid. This tank connector is not an easy part to come by, certainly it wasn't in my local DIY store and I had to order online - but really ANY configuration of plumbing bits that will let you connect the tap to the front, will seal against the stockpot wall, and attach the braiding to the back, will do the job.

This particular item is nice because the tap doesn't have to stick out any more than necessary.

4) a jubilee clip. I guess these might be known by other names in other places. I mean this:

5) a flexible plumbing hose (wide diameter type) - these are found in DIY stores and are sold for connecting Bath taps to the water pipes, and the big fat ones are best for this job. The fat ones usually have a 3/4" BSP on one end and a 22mm compression fitting on the other. Not that we're bothered about the fitments though, as we're going to be cutting them off.

6) some tools. I guess depending on what you have available to you, although you are likely to need a drill and files to make and shape the hole on the front, some spanners/wrenches etc to put the fitting on, and a screwdirver to tighten the jubilee clip.

Step 2: Make your hole in the front

Simple Self-filter Mash Tun for All-grain Beer
Simple Self-filter Mash Tun for All-grain Beer

The key here is to get the hole as low on the front as you can. The higher up this hole is, the more beer will be left inside the tun (ie wasted) when you drain it out.

Mine is about 2.5cm from the bottom of the stock pot, and in retrospect I could have got it further down.

Do yours further down.

Tips on how to make the hole: Locate the centre wisely (see above). Wear gloves. Wear eye protection (or at least keep your face out of the way gingerly, maybe squint a bit). Make a dimple with a centre-pop or a little screwdriver. Drill with a small drill first, gradually get larger sized drills in there. Mark the final circle on the steel with a marker pen, and file the hole out to that line. Remove burrs.

Step 3: Attach tank connector

Simple Self-filter Mash Tun for All-grain Beer

Push tank connector in from outside, tighten the nut.

Step 4: Attach tap

Simple Self-filter Mash Tun for All-grain Beer
Simple Self-filter Mash Tun for All-grain Beer

As you can see from these pictures, the tap screws into the front of the tank connector.

You may need to re-align the tank connector once the tap is on, so that the tap ends up vertical when screwed into its socket tight. Don't forget a bit of PTFE self-amalgamating sealing tape at this point, if you have it.

Step 5: Braid-harvesting

The flexible plumbing pipe is a rubber hose with connectors on both ends and over this it is reinforced with a stainless steel braid, which help it cope with the water pressure.

We want about 12" of braid but we don't need anything else.

Cut the ends off the flexible plumbing pipe. Grasp the rubber hose inside one end with pliers, and PUSH the braid off. It it really difficult to pull off as it tends to tighten (It's like that chinese bamboo braid finger trap game!) so using a pushing action.

Leave one end open, and close the other end by crushing it flat, then folding the braid back on itself by about 1/2cm a couple of times so it is folded shut like the old metal toothpaste tubes.

So you now have a blind ending tube of stainless steel braid.

Step 6: Attach braid to the inside of your tank connector

Simple Self-filter Mash Tun for All-grain Beer

Attache the blind-ending tube of stainless steel braid to the tank connector and secure in place with a jubilee clip/hose clip.

Step 7: Brew!

Simple Self-filter Mash Tun for All-grain Beer
Simple Self-filter Mash Tun for All-grain Beer

USE THE HOSE when draining off the wort into your brew pot!

How to get best results:

1) after steeping the grains: allow the grains to stand unstirred for about 15 minutes before opening the tap. This seems to allow the grains to settle into a natural "filter bed" and prevents the braid getting clogged with fine particles

2) if it seems to get clogged - close the tap, let everything settle for a few minutes, and the re-open

3) after hop boil: take the pot off the heat for 5 minutes before trying to drain. Something about the pressures created during boiling seems to air-lock the tubing if it's still on the heat when you drain off.


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