Pump It Up!

Pumps make great tools for brewers. They can save labor and time, and let’s face it, adding a pump is a great way to trick out your system.

Commercial brewers use large, expensive pumps to move huge amounts of liquid from the mash tun, into the kettle, through the wort chiller, and into the fermenters. But size isn’t everything. Smaller varieties can be helpful in certain aspects of homebrewing. Here’s a look at a few ways to use pumps in your brewing setup.

Recirculating Wort Chiller
Homebrewers have had great success with various wort-chiller designs, including the garden hose tube-in-tube heat exchanger (counter-flow chiller) and the immersed coil. However, these designs are usually single-pass or “once through” setups, where the water passes through the chiller once and is discarded. This can be wasteful, it can generate spills, and it can be inconvenient for homebrewers living in apartments.

Pumps can simplify immersion wort chilling applications. In this compact setup a submersible pump placed in an ice bath is connected with flexible tubing to a copper coil immersed in the vessel of hot wort. The submersible pump recirculates cooling water from the bath through the coil and back to the bath. The water picks up heat from the hot wort, cooling it down. As long as there is ice in the bath, the water temperature is close to the freezing point of 32° F.

The procedure for constructing and using this type of setup for five gallons of wort is relatively simple.

  1. Make the cooling coil. Purchase  a length of three-eighths-inch-diameter or one-half-inch-diameter copper tubing, 20 feet or longer. The rotations of the coil are made by gradually bending the copper tubing in several loops around the outside of a coffee can. Leave enough straight tubing length both at the beginning and the end of the coil assembly for tubing runs going down into and up out of the vessel. These straight lengths should be bent upward. It’s important to use a tubing bender to make these 90-degree bends. Otherwise, the tubing will become kinked, reducing the coolant flow rate and making the system ineffective. If you know someone who works in a maintenance shop or is experienced working with copper, let him or her do this work.
  2. Purchase a submersible pump (available at hardware stores). Little Giant brand pump models NK-1 or NK-2 are sufficient to provide adequate ice-water flow rates.
  3. Connect lengths of clear, flexible tubing to the cooling-coil inlet and outlet. One length of tubing connects the pump outlet to the coil inlet. Another length of flexible tubing sends the coil outlet back to the ice water bath.Clear tubing offers the added benefit of allowing you to see the fluid as it flows. The flexible tubing can be connected to the copper coil with brass compression union fittings, available at hardware stores. If the flexible tubing is soft, purchase “tubing inserts” for the compression fittings. The inserts give the soft tubing support from within, allowing the compression fittings to press down on the tubing, making a tight seal without collapsing it.Alternatively, make the connections by purchasing flexible tubing with a diameter large enough to slip over the copper tubing. Then secure the connection with hose clamps or with plastic cable ties. However, compression fittings make it easier to connect and disconnect the flexible tubing from the coil. This is important if you want to sterilize the cooling coil by placing it in the pot of boiling wort.
  4. Connect the flexible tubing from the coil inlet to the pump outlet. This must be done with a compression fitting. Typically the submersible pumps have a threaded outlet. Purchase an appropriately sized brass compression fitting to connect from the flexible tubing to this threaded outlet. Tubing inserts may be necessary if the flexible tubing is soft.
  5. Make the ice bath. A standard five-gallon plastic bucket can be used to hold the ice water bath. Put one-half gallon of water in the bucket. Immerse the pump into the water with the flexible tubing connected to the pump outlet. (The water is needed to prime the pump). Next, put ice on top of the pump, filling the bucket. At least 24 pounds of ice are needed for the job, and the bucket may need to be refilled several times as the ice melts during the wort chilling.
  6. Next, place the flexible tube from the coil outlet into the ice bath, so that water recirculates back to the bath.
  7. Chill your wort. Sterilize the coil by your favorite means, and place the sterilized cooling coil inside the vessel of hot wort. Plug in the pump and watch as the wort cools. For the first batch, recording temperature readings as a function of time may be worthwhile (say every five minutes) to determine your system’s performance.

A typical setup for chilling wort uses a Little Giant model NK-1 pump with a coil made from a 20-foot length of three-eighths-inch-diameter copper tubing. The ice bath uses one-half gallon of water in a five-gallon bucket with 24 pounds of ice. A flow rate of one gallon per minute is attained, and 4 2/3 gallons of wort are cooled from boiling temperatures to 80° F within about 25 minutes. This time could be shortened with more ice, a bigger pump, or tubing of a bigger diameter.

About Centrifugal Pumps
The submersible pump used in this setup is a type of centrifugal pump. Centrifugal pumps are widely used in industry. They are good for transferring large volumes of thin liquids when precise control of flow rates is not the primary concern.

A centrifugal pump is similar to a household fan: Fluid moves under the action of a rotating impeller, which turns at a fixed speed inside a housing. The inlet or suction of the pump is at the impeller center. Fluid at the inlet is sucked into the casing, contacts the impeller vanes, and flows out the outlet at a higher pressure. The impeller is not normally visible, being inside a solid casing.

Centrifugal pumps are simpler in design than many other pump types but have more requirements for setup and use. They must first be primed, meaning that the inlet piping and the pump housing must be manually filled with liquid. These pumps cannot be run dry and will stop pumping if air enters through loose fittings or through the inlet piping. Fittings on the inlet side must be sealed properly, and the supply vessel should never be pumped near empty. Since the impeller rotates at a constant speed, flow rate is adjusted by putting a valve on the pump outlet, which may be partially closed to reduce flow.

The vessel feeding the pump should be higher than the pump itself, and the inlet piping diameter should be as large or larger than the pump inlet. When connecting threaded sections of pipe, wrap the threads with Teflon tape (available at hardware stores) to achieve a good seal and prevent air leakage. (Wrap the tape clockwise as you face the threads). Last, there should be no restrictions in the inlet piping. Inlet piping restrictions or air leakage from improper pipe connections can allow air to enter the pump cavity. Under these conditions, or if the vessel cannot supply the fluid fast enough, the pump can be starved. The vacuum created at the inlet can become so strong that the liquid vaporizes inside the pump, thus damaging it. The pump becomes very noisy under these conditions.

Magnetic-drive centrifugal pumps are good for homebrewing. The motor and impeller are coupled with a magnetic (non-contact) coupling, and there are no shaft seals to give leaks or sanitation problems.

Standard centrifugal pumps are not submersible. In the submersible type used in the chiller setup, all electrical connections are waterproof, and a screen mask on the bottom of the pump prevents solids from entering the inlet. The impeller is inside the screen and is similar to that for the standard centrifugal pump.

The greater the pressure that the centrifugal pump works against, the lower the flow rate it can put out. There is a tradeoff: You can have high flows at low discharge pressures or low flows at high discharge pressures. High discharge pressures result when the pump has to work hard to move the fluid. This can result, for example, when using outlet piping of a very long length and/or small diameter, or if there are small-diameter restrictions in the outlet piping. For high enough discharge pressures, the flow rate drops to zero, which is called deadheading the pump. Deadheading also occurs when you shut off any valves downstream of the pump. It poses no problems for centrifugal pumps if done for only short periods (less than 30 minutes).

Advantages of the centrifugal pump are reliability and low cost. Magnetically coupled pumps are sold for as little as $60. Disadvantages are that it cannot be run dry, there is no simple adjustment of flow rate, and it must be primed before use.

Submersibles are available from hardware stores. More sophisticated pumps are sold by industrial equipment suppliers such as Grainger and McMaster-Carr and scientific equipment suppliers such as Cole-Parner.

Peristaltic Pumps
Another pump useful in homebrewing is a peristaltic pump, perfect for establishing sparge rate in an infusion mash.

Homebrewers typically rely on gravity to transfer liquids. In a common infusion mash setup grains are sparged by gravity draining hot water from the “hot liquor tank” through the lauter tun, and wort is collected below. Five-gallon batches are usually sparged within 30 minutes, requiring a flow rate of at least 600 milliliters per minute.

One objective during the sparge is to equalize the flow rate of water on top of the grain bed with the wort runoff flow from the bottom of the grain bed. If the runoff is too slow relative to the sparge, the lauter tun may overflow. If the runoff is too fast, the risk increases of a stuck runoff in which the siphoning action of the runoff flow sucks the grain bed in on itself, and the grain bed becomes compacted and impermeable to flow.

Equalizing sparge and runoff flows can be can be difficult with gravity drainage. The flow rate from a given vessel depends on the level of liquid in the vessel, and while the level in the lauter tun is usually constant during the sparge, the level in the hot liquor tank vessel may not be.

And since the flow rate from the hot liquor tank depends on the liquid level inside, the homebrewer must make continual adjustments of the outlet valves in order to equalize the flows.

A peristaltic pump can achieve constant flow rates with a single setting and few or no adjustments. This pump is a type of positive displacement pump. Unlike the centrifugal type, the flow rate is insensitive to inlet and outlet pressures over the working pressure range of the pump. The range is specified by the manufacturer and within it, each rotation of the roller assembly pumps a specific amount of fluid.

The advantages of the peristaltic pump are easy cleaning (only the tubing contacts the fluid), simple flow adjustment, and no priming requirements. However, peristaltic pumps are expensive. New pumps with sizes and features useful to homebrewers range from $150 to $400.

A good peristaltic pump choice is the Masterflex 7553-50 pump drive with a model 7021-24 pump head. This is available from Cole-Parmer, a scientific equipment company. Food-grade Norprene or Tygon tubing should be used.

More Uses for Pumps
Centrifugal pumps are ideal for rapid transfer of liquid when precise flow control is not critical. A high temperature centrifugal pump could, for example, be used to transfer hot water from atop a portable burner to a hot liquor tank elevated several feet up in a multi-tier system. This eliminates the hassles and safety problems of lifting large volumes of hot water.

A good pump choice for this application is the Teel Magnetic-Drive Chemical Solution Pump, stock number I P677, available from Grainger.

Underletting a mash means to pump water to the bottom of the grain bed. Professional brewing references and popular homebrewing books suggest this technique for fixing a stuck runoff in an infusion mash. For mash vessels with an outlet at the bottom, water is pumped back into the lauter tun through the outlet piping. The water loosens the compacted grain bed by floating it, allowing lautering to continue.

Another use for pumps is underletting a mash. To underlet, simply shut off the valve on the line that runs from the hot liquor tank to the mash/lauter tun, connect a pump to the line running between the wort collector and the mash/lauter tun, then pump hot water back into the bottom of the mash. The peristaltic pump is probably best for this operation. A centrifugal pump might be usable, but it would be difficult to control.

Filtration is used to remove yeast, bacteria, trub, and chill haze from beer or wort. Fluid is forced through a filter with pores small enough to block out these undesirables, and it requires some force to push the liquid through the filter. Homebrew author Charlie Papazian mentions using carbon dioxide gas to pump the liquid from a stainless steel cylinder through a filter. However, using a pump can be a safer, simpler alternative, and a standard plastic vessel can be used instead of a stainless steel vessel. Either the centrifugal or peristaltic pump would be suitable for this application.

Issue: April 1997