Section 1

System Overview

What Is a 3-Kettle HERMS System?

HERMS stands for Heat Exchange Recirculating Mash System. The three kettles each have a dedicated role:

• HLT – Hot Liquor Tank: Contains a stainless HERMS coil submerged in sparge water. The HLT heats the mash indirectly by circulating wort through the coil, and stores sparge water for lautering.
• MLT – Mash/Lauter Tun: Where mashing and lautering takes place. There is no heating element in the MLT — temperature is maintained entirely by recirculating wort through the HERMS coil in the HLT.
• BK – Brew Kettle: Receives wort after lautering for the boil, hop additions, and whirlpool.

Why HERMS Over Direct Fire?

In a direct-fire system, a heating element sits inside the mash tun and heats wort directly. This works, but creates hot spots, risks scorching, and requires more attentive monitoring. The HERMS approach transfers heat indirectly through the coil, which eliminates scorching risk entirely and makes temperature control far more stable and forgiving. Because there is no element inside the MLT, the false bottom can also sit very low — improving lautering performance.

How the System Flows

During the mash, the MLT pump draws wort from the bottom of the MLT, pushes it through the HERMS coil in the HLT, and returns it to the MLT via the sparge arm. The HLT heating element and controller maintain a stable coil temperature, which holds the mash temperature steady. During lautering, the HLT pump transfers sparge water into the MLT while wort flows simultaneously to the BK. Two hose connections are moved between the mash and lauter phases — this is the defining characteristic of the hose-swap approach, and in a well-planned system it takes under a minute with minimal spillage.

Why Three Kettles?

Of all recirculating homebrew configurations, the 3-kettle design offers the highest extract efficiency and greatest process flexibility. With the right controller, you can mash a second batch while the first is boiling. The clear functional separation between mashing, lautering, and boiling also makes each step easier to control and optimise independently.

The Standard Build

The standard build connects the three kettles with silicone hoses and moves two hose connections between the mash and lauter phases. It is the right starting point for virtually every brewer — simpler to assemble, easier to clean, easier to troubleshoot, and fully upgradeable later without sacrificing any component investment.

Two Pumps, Two Roles

• MLT pump (mash/whirlpool pump): Draws wort from the MLT outlet, pushes it through the HERMS coil, and returns it to the MLT via the sparge arm during mashing. Later in the session, this pump is used to fill the BK, drive the BK whirlpool, and transfer wort to the fermenter.
• HLT pump: Transfers sparge water from the HLT to the MLT during lautering. Optionally, recirculates water within the HLT for optimal heating performance. This pump only ever handles clean water and is essentially clean after sparging.

Hose Routing and Valve Placement

The guiding principle is that every valve and hose connection you will touch during brewing must be reachable from the front of the system without leaning over hot kettles. Ideally electrical cables and temperature sensor cables are our of the way in the back of the system. Think through each phase as you plan the layout:

• During mashing: Access required to the MLT outlet valve, MLT pump inlet valve, the HERMS coil outlet valve, and the sparge arm return. All should be operable without stretching.
• Transitioning to lauter: Two hose connections are moved. Close all valves before disconnecting any hose. A small amount of residual wort will drip — keep a towel nearby and make swaps above the liquid level where possible.
• During lautering: Both pumps run simultaneously. You control flow rates with the output valves on each pump. Target approximately 1L per minute transfer between kettles, maintaining 5–8 cm of water above the grain bed in the MLT throughout sparging.
• Whirlpool and transfer: Allow the wort to cool below 95°C before starting any pump on the BK circuit. The MLT pump moves to the BK outlet for whirlpool, then transfers wort to the fermenter.

Pump Priming

Both pumps require priming before they run reliably, particularly the MLT pump which faces greater circuit resistance due to the HERMS coil. The correct technique: open the inlet valve, partially open the outlet valve, then start and stop the pump 4–5 times with brief pauses between cycles. The pump head needs time to fill with liquid between starts. Once flow from the return arm is steady and bubble-free, the pump is primed. If a sight glass is fitted to the manifold, use it — no bubbles visible means the pump is fully primed. Do not run the pump continuously if it is not flowing; if it won't prime, stop and check all hose connections for air ingress.

Grain Bed Management

A compacted grain bed is the most common problem in recirculating systems, and how you design and position your valves will affect how easily you can manage it. Key points:

• Stop the MLT pump completely before adding grain. A running pump will compact the bed immediately on contact.
• Stir thoroughly when adding grain — no dry clumps. Remove the sparge arm spreader plate to give yourself space to stir properly.
• Allow the grain to rest for 5 minutes before restarting the pump. This lets the grain swell and settle naturally.
• When restarting, almost close the pump outlet valve first, start the pump, then open the valve very slowly. Opening too fast creates a pressure differential that pulls the grain bed downward and compacts it.
• At a stable flow with a well-milled, porous grain bed, expect approximately 7L/min. Flow will slow as wort becomes more viscous through the mash — this is normal and the valve can be opened further as the mash progresses.
• If the liquid level in the MLT rises during recirculation, the grain bed has compacted and negative pressure is building below the false bottom. Stop the pump immediately and stir to break it up.

Temperature Sensor Placement

Sensor placement has a significant effect on mash temperature stability. The correct location for the HLT temperature control sensor is in the tee at the sparge arm inlet — at the return point of the HERMS circuit, just before wort re-enters the MLT. This gives the controller a real-time reading of the wort temperature returning to the mash, allowing it to react immediately and prevent overshoot.

Placing the sensor inside the HLT or at the MLT outlet introduces lag — the controller only sees the result of temperature changes after they have already propagated through the mash. The thermowell in the return tee should be installed horizontally; a vertical installation causes poor flow past the probe and inaccurate readings.

The Sparge Arm

The height-adjustable and two-piece sparge arm designs serve two purposes: returning recirculated wort to the MLT during mashing, and distributing sparge water evenly over the grain bed during lautering. The sparge tube height should be chosen so the bottom sits at least 2 cm below the liquid surface after doughing in — this prevents air ingress and reduces oxidation risk. 

Physical Setup

Under-Kettle Access

All Craft Hardware kettles have bottom drain ports. The bottom valve, pump inlet elbow, and associated tubing hang below the kettle base, so clear access to the underside of each kettle is required. You have two options:

• Open brew stand (not supplied by Craft Hardware): A welded or bolted steel or aluminum stand with an open frame below the kettle shelf. The shelf itself should be a grid or slatted design — not a solid surface — so that fittings below the kettle base are fully accessible. Many brewers fabricate these from 40×40 mm aluminum channel.
• 14 cm leg extensions (available separately): Raise the kettles enough to accommodate the dip tube, elbow, and pump inlet hanging below. This is the simpler option for brewers placing kettles on an existing workbench or table.

Kettle Spacing and Footprint

The HLT can be positioned to the left or right of the MLT — choose based on your available space and preferred workflow direction. Kettle spacing is not critical in the hose-swap system; 1–5 cm between kettle rims is typical. At minimum spacing, a 3-kettle setup using 60L kettles occupies approximately 126 cm at the base and 128 cm at the rim. 

Pump Placement

Mount each pump below its respective kettle for ease of purging air. Consider splash when deciding exact positioning: wort and hot water drip from hose connections during swaps. Position pumps so that drips fall to the floor or a drip tray — not onto the motor body or any electrical connections. Keep the pump motor body shielded from active splash during brewing; never get water directly on the motor housing.

Controller Placement

The brew controller must be protected from two hazards: steam rising from open kettles, and splash from hose swaps and pump priming. Steam will degrade electronics over time and can cause immediate short-circuits in wet conditions. Mount the controller to the side of the brew stand at a comfortable eye level, with cables routed away from heat sources and wet surfaces. Never position the controller directly above a kettle.

Electrical & Controls

Professional Installation

Heating elements draw significant current — 15A per element at 230V as a baseline, with some configurations drawing more. This electrical work should be carried out by a licensed electrician. The combination of high-current circuits, metal equipment, and water is genuinely dangerous if wired incorrectly or without appropriate protection.

Circuit Requirements by System Size

Each heating element requires its own dedicated circuit. Discuss your full requirements with your electrician before purchasing elements or designing a control panel.

A Brew Controller Is Effectively Required

Manual temperature management in a HERMS system is not realistic for a normal brewing session. The HLT temperature must be held continuously throughout a mash of 60–90 minutes, with adjustments needed as wort viscosity increases and heat transfer dynamics shift. Doing this manually means standing at the system and toggling the heating element on and off by hand, watching two temperature readings simultaneously, and making continuous small corrections. In practice, mash temperature drifts unacceptably without automation.

A suitable controller wired to the HLT element(s) — using the sparge arm return tee sensor as the control input — handles this automatically. It is the single most important piece of equipment after the kettles and pumps themselves. Budget for it from the start; it is not an optional upgrade.

Controller Options

For most brewers, an off-the-shelf single-circuit controller is the right starting point. These units handle element switching, temperature sensing, and pump control in one package with no electrical knowledge required beyond connecting to a correctly wired outlet.

Whichever controller you choose, ensure the control temperature sensor is wired to the reading at the sparge arm return tee — not the HLT body and not the MLT outlet. This is the correct input for stable HERMS temperature control regardless of controller type.

Fixed Manifold Systems

A fixed manifold replaces the moveable hose connections with a permanent stainless assembly — tees, elbows, valves, and typically a sight glass — mounted to the brew stand between the kettles. The pumps are integrated into the manifold rather than hanging individually from the kettle outlets. Phase transitions are managed with valves rather than hose swaps.

What a Manifold Actually Solves

The manifold eliminates hose swaps during the lauter and whirlpool transitions. In a well-planned standard system there are 2–3 hose swaps per session, each taking under a minute with minimal spillage. Whether this is worth the trade-offs below is a question best answered after you have brewed on a standard system and identified whether hose swaps are actually a pain point for you — and not before.

The Real Trade-offs

If You Do Build a Manifold

Key design principles to get right from the start:

• Keep it compact. Every additional elbow, tee, or valve adds resistance, heat loss, and a surface to clean. Use short stainless sections within the manifold core and silicone hose for the longer runs to kettle ports.
• Design drain points in from the start. Every section of the manifold that can trap liquid needs a drain — either a dedicated drain valve or a removable end-cap.
• Mount the manifold to the stand, not to the pump bodies or kettle fittings. The combined weight of the manifold and pumps is significant. All of this load must transfer to the stand.
• Use 1" fittings throughout for an 85L system. A manifold must not become a flow restriction. Undersized fittings embedded in a fixed assembly are far harder to change than an undersized hose.
• Standardise valve handle orientation. All closed handles pointing the same direction — consistently all up or all down — so valve state is instantly readable at a glance.
• Do not preload fittings. All components must come together without force. If you have to pull or push sections to mate them, the assembly is under mechanical stress that will cause leaks and crack fittings. Adjust table clamp positions until everything aligns freely before tightening.

Kettle Selection

Available Sizes

Craft Hardware kettles are available in three sizes. All have bottom drain ports. Volumes below are usable working capacities:

All kettles use DN40 Tri-Clamp ports throughout — 50.5 mm flange, 38 mm inner diameter. This is consistent across all three sizes, making every fitting, valve, and hose interchangeable across the entire range.

Tri-Clamp Sizing

What Is Tri-Clamp?

Tri-Clamp (also called Tri-Clover) is a hygienic pipe connection system originally developed for the food, dairy, and brewing industry. Two identical flanges are joined by a clamp with a gasket between them. There is no male/female distinction — both sides of every connection are identical and fully interchangeable. Assembly and disassembly is tool-free or nearly so, and every connection can be visually inspected for cleanliness.

For brewing, this means no threads to trap bacteria, no PTFE tape, and the ability to disassemble, clean, and reconfigure the entire system without special tools.

Fitting and Hose Sizing — Recommendations

Matching fitting and hose size to your kettle class is important for both flow performance and cleaning. Our recommendations:

The 1.5" × ¾" fitting used in the 40L and 60L class has a 1.5" Tri-Clamp flange — compatible with all DN40 kettle ports — and a ¾" tube size or hose barb. This is the right balance of flow rate, pump compatibility, and cleanability for these kettle sizes.

For the 85L class, the larger volumes benefit from the full 19 mm bore of the larger tubing and 22.1mm ID of the 1" fittings. Using the smaller fitting size on an 85L system will create a meaningful flow restriction, which is particularly problematic in the HERMS coil circuit where resistance is already the highest point in the system.

Gasket Sizing — The Critical Rule

The gasket inner diameter must match the inner diameter of the fittings being joined. A gasket that is too small protrudes into the flow path, creating a ledge that traps debris, causes turbulence, and resists cleaning. In a hose-swap system this is a minor inconvenience. In a CIP manifold circuit it is a serious problem — cleaning solution flows around the ledge rather than scouring it, leaving residue that supports bacterial growth.

The rule:

• When joining two fittings of the same inner diameter: match the gasket ID exactly.
• When joining two fittings of different inner diameters: select a gasket whose ID matches the larger of the two fitting IDs. This keeps the flow path fully open at the connection point.

Specify the actual inner diameter of each fitting — not just the Tri-Clamp size label — when ordering gaskets. If you are unsure, contact us before ordering.

Gasket Materials

Silicone Hose Installation

Silicone hose is stiff at room temperature and difficult to push onto a correctly sized barb fitting. It relies on a good interface fit to prevent slippage. Do not match the ID of the tubing to the OD of the hose barb. Always fit a stainless hose clamp over every hose-to-barb connection. Do not rely on the interference fit alone, particularly on pump outlets where positive pressure is present during operation.

Cleaning

First Use

Before the first brew, run a full cycle of brewery cleaning solution (e.g. Chemipro Oxi, PBW, or similar — nothing chlorine-based) through all components, followed by a thorough rinse with clean water. This removes manufacturing residues, oils, and any debris from the assembly process.

Hose-Swap System — Post-Brew Cleaning

The hose-swap system is straightforward to clean, which is one of its underappreciated advantages. After sparging is complete, the HLT has only ever held water and is essentially clean — disassemble, towel dry, and set aside. The HLT pump is also clean and should be stored inverted to drain completely.

For the MLT and BK:

• Flush all circuits with hot water while still warm from brewing — residue cleans far more easily when hot.
• Disconnect and clean silicone hoses separately; inspect for discolouration or off-smells.
• Remove and disassemble the pump head; rinse carefully with clean water. Do not wet the motor body.
• Unclamp and rinse ball valves; towel dry and reassemble.
• For the kettle bodies, a hot water rinse and soft sponge is sufficient after a normal session. Use PBW or equivalent for a periodic deep clean.
• Towel dry all parts and allow to air dry fully before reassembling for storage.

Fixed Manifold System — CIP Cleaning

A fixed manifold cannot be disassembled for cleaning after each session. It requires Clean-In-Place (CIP) cleaning — circulating hot cleaning solution through the entire assembled circuit. This is the standard approach in commercial brewing, but it adds meaningful time and effort to every brew day.

• Add water and your chosen cleaner to the HLT. Heat to the temperature recommended by the manufacturer.
• Recirculate within the HLT circuit for 5–10 minutes.
• Pump cleaning solution through the HERMS coil into the MLT; recirculate the MLT/HERMS loop for 5–10 minutes.
• Transfer to the BK and recirculate through the whirlpool loop for 5–10 minutes.
• Drain completely. A final water rinse is optional but recommended (depending on your cleaning product of choice).
• During CIP, cycle each ball valve open and closed several times to ensure cleaning solution reaches and scrubs the valve seat. A valve left in a fixed position during CIP will have residue on the ball and seat.
• Leave all valves open and drain ports uncovered to allow complete drying.

Pump Head Maintenance

Regardless of system type, periodically disassemble the pump head from the pump body for a thorough clean and inspection. Inspect the impeller for wear, cracking, or debris. Do not overtighten mounting screws of clamp when reassembling. Allow the head to dry completely before reinstalling.

What Not to Use

• No bleach-based cleaners on stainless steel — they cause chloride-induced pitting corrosion that is permanent and irreversible.
• No abrasive pads on kettle interiors or exteriors — fine scratches can mar the finish and appearance of your kettle.
• No dishwasher for silicone hose or gaskets — the combination of high temperatures and aggressive detergents degrades silicone over time.