The "GL Plumber's Delight" vapour condenser

For Sale The original plumber's delight condenser, featured on this page, which led to the development of the GL and Push-Pull processors, is available for sale. Excellent condition, first class working example, has made many thousands of litres of fine biodiesel and inspired many to try their hand at the craft.
Feb 21, 2014

This is a simple, compact condenser which you can make in an hour or two using standard soldered plumbing parts. It can also be made with compression fittings.

It takes up very little space and is efficient, using less water than a conventional straight-through still.

It does this by making the vapour and water streams turbulent, so that they avoid a hot 'core' of vapour forming down the middle of the condenser or cold water on the outside of the water jacket. We are trying to avoid laminar flow, typical of most straight condensers. And we are trying to use less water than a coiled condenser would use.

To create the turbulence, I crimp the inner condenser pipe at regular intervals, at alternate 90 degree angles. See the pics for clearer understanding.

There is very little water in the jacket, the aim being to have fast, low volume water flow with good heat transfer.

I use my reaction vessel to heat BD to drive off the surplus methanol, after the glycerine has been drained off.

I keep the circulating pump running at all times, and this helps to make the whole process faster and more efficient.

After 4 or 5 batches, I put my stored glycerol into the tank, to recover methanol. Pre-heat your glycerol to around 50C before you put in the tank, or its viscosity may be too high for your pump.

IMPORTANT: ALWAYS fill the tank before you switch on your heating element. Never use a partial load if there is ANY chance you could have any part of the heating element above the liquid level. This could cause an explosion.

Here's the finished article being fitted to the reactor....

And here's what you need for a 100 litres load, heated with 3kW. Make longer for more heat input/less load....

4 x 44mm long bits of 22m dia copper tube...

2 x 22mm female tee joints...

4 x 22mm to 15mm female reducers...

A 1 metre length of 22mm copper tube for the outer jacket...

A 1.25m length of 15mm copper tubed, crimped at 90 degree intervals...

Here's a closeup of the crimped pipe...

I used a pump wrench to squash the pipe. Make sure you don't squash it too much - have a small piece of 22mm pipe handy and make sure it will slip freely over the crimps you make. I made mine ever-so-slightly an interference fit in the 22mm pipe, but it was very easy to slide the completed crimped 15mm pipe into the 22mm jacket.

Nick (Twenty4Seven) made a good suggestion - Use adjustable mole-grips to set the crimp depth, so that all crimps will be the same.

You can see how this crimping makes an effective turbulence generator for both the water and the methanol vapour...

The vapour forms a thin rectangular jet, lets say north-south. Then it has to suddenly change to an east-west rectangular jet, and so on, repeatedly down the length of the pipe.

This causes it to make intimate contact with the pipe walls, preventing the effect of having a hot central core of vapour.

I now have 2 thermometers running when I distil...

1. Thermometer to measure vapour temperature into condenser. Aim = 65C. When it rises to 70C I stop heating. You can run higher, but may find you get too much water in the methanol.

2. Thermometer to measure main tank liquid temperature. Start at 65C. If it reaches 90C I stop heating, but you can take it further - but perhaps with less purity if you've done a prewash.

You'll find you reach a point where the system stalls and no more condensate appears even though there may still be methanol in the BD. This is because it is mixed, and it's boiling point has risen to a temperature above that to which you have heated.

A useful post which discusses this phenomenon is here.

You can recover a little more methanol from the biodiesel after 'normal' distillation stops, by injecting a very slow air stream into the tank. This would normally be via the venturi inlet, using valve V4 if you have an EcoSystem processor.

Keep the heater on and the pump running. Start with a VERY slow air feed, and you will see that methanol liquid appears again at the condenser output. Gradually increase the air rate, until the methanol output speed decreases. The output will decrease if you inject too much air, because the air will carry methanol vapour away with it. Reduce the air to a point which gives optimum methanol recovery.

Eventually, you will reach a point where no more liquid methanol appears. This is because the dewpoint of the vapour is higher than the temperature of the cooling water. You can now put a lid on the methanol collecting vessel. Do NOT block or seal the condenser outlet.

You can now increase air inlet to remove the small final traces of methanol.

Good luck, hope it works as well for you as it does for me.

Graham Laming

How to solder Copper fittings
Thanks to ViewDo for this introduction...

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