Recirculation Pump

The Recirculation Pump is what differentiates the recirculation mashing systems from all the others. The Recirculation Pump takes wort from the bottom of the Mash Tun, pumps it through the Heat Exchanger and the back to the top of the mash. This allows precise control of mash temperatures plus the benefit of setting the grain bed early and using the constant recirculation to obtain crystal clear runoff. Since the wort must remain somewhat sanitary, it is important to use a magnetically coupled pump. This type of pump uses a magnet to couple the drive shaft with the impeller. This allows only the impeller to touch the wort.

The key issue on this component is deciding which pump to get. I bought mine from Moving Brews however, as of 12-26-01, the company has stopped taking orders and have pretty much dropped off the radar screen. Try Grainger or McMaster-Carr and look for Little Giant, or March brand magnetic drive pumps (there are other brands also). I bought a March pump, I think the actual March model is MDXT-3. This pump has female NPT threads on the inlet and outlet. I think this is the best set up since most of your fittings that you will use will have male threads on them. I would not recommend the pumps with the barb/slip fit connections that require a hose clamp (big surprise, eh?). Eventually, you will want to change out a hose or reconfigure something and getting the hoses off can be a real pain. Also, this does not allow you to remove your pump from your system. Female threads offer the most flexibility for change later on.

As you can see, I have quite a bit of plumbing attached to the pump. At each connection point, I use quick disconnect fittings. I highly recommend these. There are more details on these on the Plumbing page.

The inlet of the pump is in the center of the pump housing. Here I have two inlet connections. One goes to the recirculation valve on the Mash Tun, the other one goes to the HLT. I do not have any valves at the pump inlet since there are valves at each of these connection points on the Mash Tun and HLT. There is also a more important reason for this, but I'll cover that later.

On the outlet of the pump I have two outlet valves/connections. The valve that has the quick disconnect fitting gets connected to the inlet line on the Heat Exchanger. The other valve is only used to prime the pump. The magnetically coupled pumps are NOT self priming. This means that the pump must be mounted BELOW the inlet source of liquid or else the pump will not work. There must be a positive suction head on the pump for it to work. In addition, the pump housing must be able to fill with liquid BEFORE the pump is turned on. I have my pump mounted vertically so that the priming valve is pointing straight down. To prime the pump, I put a container below this valve, then open the valve for several seconds until I get a good steady flow, then shut the valve. The housing is now completely primed. This is especially important when recirculating wort. If there is any air inside the pump housing, the pump will whip air into the wort which is not desirable.

Another important aspect about the pump is the proper way to meter the flow rate. Sometimes you don't want the pump to pump at its full flow rate. This is accomplished by restricting the OUTFLOW of liquid from the pump via a valve. Never restrict the liquid inflow on the pump. By doing this, the inlet pressure on the pump will fall below the vapor pressure of the liquid and the pump will cavitate. Cavitation doesn't whip air into the beer, but it's really hard on the pump and can damage it. Always meter the flow by adjusting the OUTFLOW of the pump. You can even leave the pump running and shut the outlet completely off for a short period of time, the pump doesn't care.

DO NOT attempt to use a speed control on the pump to meter flow, the electric motor is made to run at the rated voltage and current, altering these specs can burn up the motor. I've read more than one account where someone did this and ended up buying a new pump. Meter the flow with the outlet valve.

Notice on my pump plumbing that there are no valves at the pump inlet. I did this to make sure I never accidentally used a valve on the inlet to meter the flow.