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Many homebrewers endeavor to brew with the utmost precision. If that describes you, it’s time to embrace your inner engineer and take a further look at two similar brewing systems that will enhance your mashing.

Both RIMS and HERMS are brewing equipment systems. They allow a brewer to hit a target mash temp exactly, maintain a specific temperature, and ensure that the temperature is consistent throughout the mash. They also enable brewers to perform step mashes without difficulty.


What is RIMS?

RIMS stands for “recirculating infusion mash system”. It is a system that enables a brewer to have complete control over mash temps.

One type of RIMS allows you to hold or raise the temperature of your mash via heat applied to or in the kettle. Those systems are usually referred to as kettle-RIMS. Kettle-RIMS can be heated via electricity or propane gas.

In a typical RIMS, wort is piped through a coiled metal tube that looks like an immersion wort chiller on a small scale. As the wort flows through the metal piping, heat is applied. In electric systems that use ultra low watt density elements, you can’t scorch the wort. Scorching can occur in other systems that use a gas burner to apply heat. It can also happen if your electric system isn’t employing an ultra low watt density heating element.

In addition to adding heat for the purpose of maintaining a temp or raising it, RIMS recirculates the wort. Wort is recirculated from the bottom of the mash tun back to the top, thus, allowing for an even distribution of temperature and better clarification.

In a RIMS, the pump is on the entire time while the heating element turns on when heat is needed but remains off otherwise.

What is HERMS?

HERMS is an acronym for “heat exchange recirculating mash system”. The outcomes of using a HERMS are the same as RIMS. That is, it heats and recirculates your wort while mashing.

HERMS differs from RIMS in the way heat is applied to the mash. With HERMS a metal coil is placed in the hot liquor tank (HLT) and wort from the mash is pumped through that metal piping. In this manner, heat is transferred from the water in the HLT to the wort flowing through the metal coil and back to the top of the mash tun.

In a HERMS, heat is constantly “on” due to the placement of the coil in the HLT but the pump turns on and off as heat is needed.

The Key Difference Between RIMS and HERMS

Upon first glance, the difference between RIMS and HERMS is confusing to many brewers. We already went over this briefly but it bears repeating.

In an article from beerandbrewing.com, expert Brad Smith says, “RIMS systems run the pump continuously and vary the heat source, while HERMS systems turn the pump on and off to control the temperature, drawing heat from a fixed source such as the HLT.”

Advantages Over RIMS

When using a HERMS, you avoid the potential of scorching your wort. This is because you are applying heat via a heat exchanger, typically in the hot liquor tank. But scorching is usually only true for gas powered RIMS.

Pros for RIMS and HERMS

Here are the real benefits from using a RIMS or HERMS.

Constant and Exact Mash Temps

There are some obvious reasons for getting a RIMS or HERMS. The main advantage is the ability to target mash temperatures and hit them with precision.


You’ll find both automated and manual systems. Regardless of how you control it, flipping a switch or pushing a button to raise or set your mash temp is a nice feature. Using a RIMS or HERMS really takes the feeling of guessing out of your brew day. You know you’re going to hit your target temps…exactly

Step Mashes

These systems are also really nice if you do or want to do a lot of step mashing schedules. Stepping from one temp to the next is a breeze. Just push a few buttons and you’re good to go.

Cons for RIMS and HERMS

There are a few drawbacks to using a RIMS or HERMS system.


These systems are expensive to build and more expensive to buy. If you’re purchasing a full on brewing system, expect to pay $4,000 on the low side. That said, many brewers with metalurgi talents and ingenuity can cob together elaborate and effective systems on a shoe-string budget.


We all love cleaning right? More pipes, pumps, and hoses means more time spent cleaning and less time for something more meaningful. If you’re already trudging through cleanup after a brewday, consider keeping things simple. These systems may not be for you.


If you’re one of the few brewers these days that loves decoction, then RIMS and HERMS are definitely not for you. Flavor impact aside, you effectively eliminate the need for decoction mashing with the ability to perform step mashes with ease.

Myths Concerning HERMS and RIMS

I’ve come across some brewers talking about how a huge advantage of these systems is repeatability and consistency. There are a few situations where using a HERMS or RIMS will allow for improvements in these areas. Namely, if you brew in extreme climates with big seasonal temps changes.

That said, gadgets don’t mean more consistent or better outcomes. You can achieve very consistent and repeatable outcomes by simply taking notes and repeating what you did before. The bottom line is that if you keep the variables the same, your outcomes will be consistent and repeatable. And if using a HERMS or RIMS helps you do that, more power to you!

Final Thoughts

RIMS and HERMS are useful. If you derive a lot of joy in brewing from designing elaborate brewing systems, give these a closer look. On the other hand, if you’re happy with your BIAB setup and the results you get with that, that’s great too. One reason homebrewing is so much fun is the fact that there are many “right” ways to make the best beverage in the world.

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