HERMS Brewery

I decide to build my HERMS back in 2006 after seeing so many fantastic breweries on the internet (almost all American and not one in the UK). I had been brewing for many years and my plastic brewing equipment was starting to fail on me. The last straw was when, during one session, the boiler wouldn’t boil. I emptied the wort into a fermenter to have a look at the element and the fermenter split depositing a gallon of lovely wort on my garage floor before I got to it.

That was it, I was going to have one of those stainless steel jobbies like I’d seen on the internet.

Well, first off I searched the internet for the best ready made home brewery and discovered the B3 models from Morebeer. However, the cost of these systems is kind of high when you factor in the shipping to the UK from the US and any customs charges. Therefore there was only one thing to do. Build my own!

It took me a couple of months to build and the majority of this was spent sourcing the necessary parts. Back then there wasn’t easy to find the right parts. Certainly the home brew shops didn’t stock things like weldless bulkheads. The situation’s getting better, thanks to the internet improving visibility of the variety of products available in the US, but back then I was on my own.

My HERMS consists of 3 stainless steel vessels; one for the HLT, one for MLT and another for the copper (boiler). The wort is recirculated with a pump through a heat exchanger. A second pump is used to sparge with the liquor from the HLT. Ball valves control the flow of the wort and liquor.


The whole system is mounted on a mild steel stand. I’ve tried to keep the design very simple to enable cleaning and ease of use/repair. I have brewed many batches on this brewery and I believe it to be a well thought out and robust design.

Take a look at the sub page links on the right hand panel of this page to see each of the different parts of the design.


I’ve been brewing beer for over 20 years. Having started off brewing from malt extract kits I’ve progressed through all-grain brews to where I am now; brewing all-grain on a stainless steel, temperature controlled HERMS brewery.


I got the pumps from ebay for about 27 quid each. They are used but are perfectly clean and serviceable. They are Totton GP20/12’s which are magnetically coupled so that I can control the flow with a ball valve on the “out” side without causing stress on the unit.
I use one pump to pump the wort and another to pump clean water for doughing in and sparging. A lot of people seem to use just one pump but this only works if you batch sparge or if you use gravity for sparging in a fly sparge system.

These spinny spargers as in the photo below are no longer imported to the UK so once mine finally wore out I moved to using my return manifold to add the sparge liquor but I still fly sparge of a fashion. I’ve not noticed any impact on efficiency at all in using this method so I’ll stick with it.


240vac is very dangerous and you should never mess with it unless you’re confident that you won’t kill yourself.

Most of the electrics are housed in a waterproof box. Any connections outside this box are waterproof in their own right. With all the water and wort flying around on brewday this is a really good idea. I originally mounted the controls on an aluminium plate with the connections exposed on the back but I popped several PID controllers by splashing them so I fitted the waterproof box.

The way I connected my electrics up, I only break/make the live feed to the element with the SSR. To be sure that the element is completely isolated you could (and arguably should) also break/make the neutral with a second SSR.

Here’s a diagram showing the system connections. It’s really very straight forward but if you have any doubts get an electrician to do it for you.

The SSR I use is a Tyco SSR-240D25 which I bought from RS. The spec is in the name; it’s an SSR used to switch 240 vac, it’s switched by a DC voltage and it’ll switch 25A. The element in the heat exchanger is a 2.4kw unit and it’ll draw 10A max, so the SSR is well able to switch it on and off safely.

The thermocouple is designed to be attached to a pipe with an attached jubilee clip. It’s a K-type thermocouple and I have attached it to the pipe exiting the heat exchanger. This is what they look like (in the RS catalogue).


The copper is the vessel in which the wort is boiled together with the hops.  It’s basically a 75l stainless steel vessel with two 3kw, 240vac elements and a hop stopper made of 22mm copper leading to a ball valve.

As soon as the wort covers the first of the two elements I switch on the power. This means that the boil commences even before all the wort is collected.

Once all the wort is in the copper it is boiled fiercely to produce the “hot break” which is the proteins coagulating in the copper so that they can settle out later.
After about 60-120 minutes of boiling, the wort is cooled. I’ve been using a plate chiller for the last 2 years. It gets the wort to pitching temperature very quickly. Concerns expressed by other brewers about the ability to keep it clean seem to have been unfounded.

Heat Exchanger

The heart of any HERMS is the heat exchanger.

Many people put a coil of copper in the HLT and use a PID controller to control the recirulation pump to maintain the set temperature in the mash tun. I don’t like this idea as my HLT holds, typically, 60-70 litres of sparge liquor.

This volume of water cannot be controlled quickly enough to react to any temperature change required. This is why I designed and built my own heat exchanger that holds just under 4 litres. This can be heated with a single 2.4kw element from 20°C to boiling in a matter of a few minutes.

My first heat exchanger was made from a 30cm length of 100mm copper pipe. I sealed one end with a disc of copper sheet (glued on with JB-Weld) then drilled this and fitted a 2.4kw kettle element. I then made a coil of 8mm copper pipe and stuck it in the other end of the pipe and filled the 100mm pipe with water.

This heat exchanger worked fine in the summer but weather cooled down I found it didn’t really have the flow to keep the mash tun at the right temperature. I finally replaced it with a 150mm diameter copper pipe and a coil made from 10mm copper (previously a Brupaks immersion chiller). This enables me to recirculate at a higher flow rate.

The heat exchager is what the wort is pumped through in order to maintain the mash temperature or to raise it for step mashes.

The power to the kettle element in the heat exchanger is controlled by a PID controller and a solid state relay.

The PID controller is a great piece of kit. It uses a mathematical algorithm to compare the desired set temperature to a measured temperature taken from the outlet of the exchanger. The bottom line is that I set 66°C and the kettle element comes on until the measured temperature matches it.

It’s not quite that simple as I also have to set the differential between the temperature measured and the temperature in the mash tun but you get the idea!

Mash Tun

The mash tun is where the starches in the grain are converted to sugar to be fermented later by the yeast. In this system the mash tun takes the form of a 100 litre stainless steel vessel. I have made a slotted manifold from 22mm copper through which the wort exits the mash tun for recirculation or running into the copper. On the underside of the manifold are slots cut every 10mm with a hacksaw.

Here’s a couple of photos of me doughing in which is the process of mixing the grains with water heated to strike temperature. Strike temperature is dependant on the temperature of the grain and the thermal mass of the mash tun. Typically to get a mash temperature of 66-67°C I need the strike temperature to be 75°C. This temperature will vary from system to system depending on how well insulated the mash tun is and whether you preheat it.

It’s worth noting that the mash temperature remains very stable in my system even without the recirculation purely due to the thermal mass of such a large amount of grain. I can mash 15 kg + of grain and it will remain at 66-67°C for well over an hour even without insulation.

Once I’ve doughed in I let the whole mash sit for a few minutes before I commence recirculation. This pause allows the grain to take up the liquor and settle down into a stable mash bed so that, when I start the pump I don’t suck grain into the recirculation system.

Recirculation is carried out by pumping the wort from the mash tun, through the PID controlled heat exchanger and back through the return manifold.

Here’s a photo of the return manifold in action.  This photo was taken after just a few minutes and already you can see the clarity of the wort.

After an hour or more of mashing all the starch is turned to sugar so it’s time to start the sparge.

Sparging is the process whereby the sugars are gently washed from the grainbed in the mash tun. There’s a couple of ways you can do this; batch sparging or fly sparging.

I used to fly sparge which means that I sprinkled hot water on top of the grain bed whilst pumping the wort to the copper from the bottom of the mash tun. Batch sparging is achieved by effectively mashing twice and running off the wort completely each time. There are benefits to each method of sparging; batch sparging lessens the probability of extracting tannins due to the fact that the pH remains lower than when fly sparging but fly sparging is more likely to give you a better quality of wort due to the ability to cease sparging earlier. I’m sure the batch spargers out there will dispute that statement but this is my page so I’ll write it how I find it!