A Bilge Pump to Clarify Wort: Projects

When I was finished fabricating my backyard half-barrel brew system, I knew there were more gadgets that could be added. The set-up was great, but I wanted more! Some sort of quasi-RIMS (recirculating infusion mash system) seemed the likely next step.

There seem to be a lot of homebrew-magazine articles these days about RIMS-related topics. But the store-bought systems that are available — the kind that pump the wort out of the mash tun, run it through an electronically-controlled inline heater and return it to the mash — cost more than the average homebrewer would want to spend. And building your own full-blown RIMS requires the ability to work with complicated electronic components.

I knew I could design a pseudo-RIMS with easily found components. It would be relatively simple to build at home and it would cost a whole lot less. No, I wouldn’t have the electronic temperature-control system with all the bells and whistles, but my system would be almost as effective.

The purpose of a standard RIMS is to allow homebrewers to easily raise and control the temperature of their mash without overshooting the target temperature. My brew system is extremely well-insulated, and I have no problem keeping the mash temperature steady — even when brewing outdoors in winter. So controlling my mash temperature wasn’t an issue. Still, I wanted a pump that would recirculate my wort during the mash to clarify it, which would eliminate the need for a separate “vorlauf” (recirculation) step after the mash. When the mash was over, I’d have crystal-clear wort ready for the brew kettle.

The first step in this project was to find a pump that would be cost-effective and also do the job. It had to withstand temperatures of 150° to 160° F. After looking through numerous catalogs and visiting local air-conditioning and plumbing supply shops, I learned that a suitable pump would cost around $100 to $200. After extensive research on where to find a pump that would cost less, an idea popped into my head: Why not use a bilge pump, the kind that’s commonly used on boats? I took a ride down to the local boat shop and found many pumps that were suitable. The prices ranged from $20 to $35. (A safety note: I didn’t ask whether the bilge pump was made of food-grade plastic, and to be honest, it doesn’t really worry me. If you’re concerned that something nasty might leach into your beer, be sure to locate a food-grade plastic pump for your own system.)

Would the pump withstand the heat of the mash? After brewing with mine, I found that it did. My pump operates on 12 volts DC. The other bilge pumps I saw were all powered by the same voltage. So I needed a converter. Luckily, 110-AC to 12-DC power converters are available inexpensively at electronic shops like Radio Shack. A common battery charger might also suffice.

The inlet of my pump is threaded in standard plumbing half-inch NPT. My half-barrel brew system (affectionately known as “The Brewpig”) has a ball valve threaded the same, making a retrofit a simple job. I added a threaded brass half-inch “T” fitting between the mash tun exit ball valve and the bilge pump inlet. The exit of the pump is threaded to 3/8 inch NPT. I attached a threaded fitting to the exit port of the pump and connected a short length of copper tubing to it. I ran the tubing up the outside wall of the mash tun and bent it into a loop that goes over the top and into the mash tun. I attached a short length of plastic tubing that would lie on top of the grain bed. This would prevent any excessive splashing of the recirculated wort, which could cause hot-side aeration.

When testing my wort pump for the first time, I found that the initial gulp from the mash tun into the pump was almost all grain. This plugged up the exit tube. To remedy this, I placed an in-line screen filter between the exit of the pump and the looped tubing. After the initial operation of the pump, I would disassemble and clean the grain out of the screen filter. This ensured that the system would not plug up again and would run very nicely, filtering out most, if not all, of the grain hulls and residue. After this modification, the wort would run very clear to the brew kettle.

I would operate the system for 5 or 10 minutes at a time throughout the mash cycle. My mash temperatures tended to vary by little more than 1 or 2 degrees F during the mash sequence. By the way, my mash tun is insulated with ordinary foil-covered duct wrap (the type used to insulate hot air ducting) and has a propane “Cajun cooker” burner under it. It also has a motorized mash mixer. All of these features help keep my mash evenly mixed and evenly heated. I never have to fire up the burner to maintain temperature, but it is an option, especially in a step-infusion mash.

This system is simply a recirculating device, designed to clarify your wort. There is not any temperature control. But after brewing a few batches, I found that there was an insignificant amount of heat loss from the pump or recirculating tubing. I had briefly considered insulating the entire assembly, but eventually found it to be unnecessary.

This system was built to fit my half-barrel home brewery that uses old Sankey kegs, but it could also be adapted to a tabletop mash tun of your own personal design. With a little ingenuity, some commonly found plumbing fittings and plastic tubing, you could mount a small bilge pump onto the side of a picnic cooler and simply re-circulate your wort back into it. There are endless combinations that the homebrewer can experiment with. If you use your imagination, you can design a system that suits all of your needs.