The following posts assume you have an espresso machine intended to be plumbed in, either setup for direction connection only or a switchable machine that can either be plumbed in or tank fed. 

Why Plumb-in?

This is the first post in this series discussing what I learned throughout the process of plumbing in or directly connecting my espresso machine to a water source.  I guess the logical first place to start is why you would want to plumb in your espresso machine and what, if any difference it makes. 

You Need Water!

The first and most logical reason of why someone would want to plumb in their espresso machine is so they never run out of water!  This may seem really trivial and petty at first, however, if you’ve ever had the pump and boiler of your tank fed machine cut out mid-shot because the low water sensor kicked on, you know the frustration (some espresso machines are nice enough to let your shot finish).  Another huge advantage for most is that it’s typically not easy to refill tank fed machines because most access the water reservoir via the top of the machine, and if the machine is located under cabinets, access can be restricted or tight.  And, you won’t risk actually running out of water.  I will touch more on this later, but specifically if you’re buying bottled water to control the quality, you will not have to worry about running out of water, and risk filling your machine with poor quality water. 

Preinfusion

The next main reason for plumbing in your espresso machine is to change the performance.  Many rotary pump machines that offer preinfusion or the ability to control preinfusion require the machine be plumbed in to a water source, with many relying on the line pressure of the water itself to deliver the preinfusion water.  Without getting super deep into the topic, preinfusion is kind of like the bloom process in brewing coffee; allowing the grounds saturate and expand with a smaller amount of water before the brewing commences.  For espresso, this is typically done at a much lower pressure than the actual extraction and is said to promote a more even extraction, which can make it more forgiving of technique, equipment, or coffee, and increase extraction or improve flavor.  There is also discussion regarding using preinfusion to soften acidity in the coffee, or taken to extremes with extended preinfusion or pre-brewing, can allow a user to increase extraction by grinding finer and wetting the coffee at a low pressure before the full extraction begins. 

This can be done in many ways, depending on the design of the machine and the control it offers.  In the case of many home users, myself included, plumbing in the espresso machine to allow line pressure preinfusion, will also allow pressure profiling of sorts to explore the minutiae or the really fine tuning of extraction.  Many home / prosumer espresso machines utilize the E61 brew group, so for simplicity sake, let’s look at it from that standpoint.

The E61 group, by design, contains a chamber for water that needs to fill before the brew chamber pressurizes during extraction, offering built in preinfusion in the sense that not the full brew pressure hits the bed of coffee immediately – there’s a ramp up over the course of 3 seconds or so.  The design is such that the cam actuated lever also has a middle position of sorts where this chamber is open, but the pump is not yet engaged.  When this happens, water will be “passively” fed at the inlet or line pressure of the water source, typically 2-3 bars of pressure, this is preinfusion.  If this same machine is being tank fed, some water will be delivered from the pressure of the boiler, but it will be merely a trickle.  This is commonly referred to as “pre-wetting”, though I’m not convinced pre-wetting does anything to influence the extraction since it’s such a small amount of water barely saturating the top of the puck (though I don’t think it has any adverse effects). 

This middle position of an E61 equipped machine can be used on the tail end of a shot as well to ramp down or provide a declining pressure profile of a shot, more similar to that of a traditional spring lever machine.  Since the middle position allows water to continue to flow without the aid of the pump, and without activating the 3-way solenoid that exhausts any water remaining in the brew chamber, you can cut out the pump towards the end of a shot and either allow the extraction to continue at the lower water line pressure (if directly plumbed) or at boiler pressure (if not plumbed), essentially allowing any remaining water in the brew path to continue through the puck before ending the shot.  I don’t think this will dramatically change the results in the cup of a particular coffee, but it can be used to “soften” the tail end of an extraction, which can aid in decreasing the likelihood of over extracting, or in the case of light roasts that are easy to under-extract, this can allow the tail end of shot hold on for a little longer by slowing down the flow and increasing the overall extraction time, which can help to reduce acidity or increase extraction and “round out” the profile.  It’s important to again stress that this is really looking at the last little details of dialing in and bringing out the fullest potential of a coffee, as this won’t dramatically change the results, but it’s sure fun to play with as an additional variable, and that what we’re here for anyways right?

Control Water Quality

One of, if not the biggest enemy for an espresso machine is poor quality water, specifically using water that causes scale and/or corrosion.  The coffee you make can only be as good as the water you start with and optimal coffee does use water with specific values.  The water should have some TDS (total dissolved solids) or mineral content so it tastes better and extracts well, the hardness should be low (both general hardness and carbonate hardness), and the pH of the water is also important for balance, along with other factors like alkalinity, chloride, other chemicals, etc.  So, unless you’re lucky enough to live somewhere that happens to have “good” quality water (for coffee/espresso brewing), the water you use should either be treated to fall in the target range or purchased, to avoid causing any scaling and/or leeching of metals in the machine or unwanted flavors.  By using water that has the “optimal” properties you can potentially avoid ever needing to descale the machine, increase the longevity of the machine and its parts, and improve the taste of your coffee.

I purchased a switchable machine, or one that can be tank fed or directly plumbed with the intention of plumbing the machine in when the time was right.  Shortly after, we decided we would eventually move to a bigger house, so I held off on plumbing the machine and instead used Crystal Geyser (CG) bottled water.  The CG water in my area comes from their Mt. Shasta bottling facility, and the properties of that water are pretty good for brewing quality and also for not promoting any scale in the machine.  As much as I don’t like using bottled water from a sustainability standpoint (both environmentally and monetarily), it made sense to protect the investment of the machine.  I typically used a gallon or less a week, with pricing on average at $1 per gallon.  Plumbing the machine in has been so nice as to not have to purchase gallons of water at the grocery store, or worry about running out of water, or forgetting to fill the tank.  I think it can also help promote better cleaning practices since you're not as reluctant to flush the group and boiler and empty the tank for routine cleaning.   

Researching what water treatment system to use when building a wet bar at my house proved to be very interesting, humbling, and educational.  Be sure to check back for the next post in this series discussing water treatment options for home espresso machines.  Following that post, we will also cover other things to think about when positioning, installing, and setting up, as well as overall thoughts, takeaways, and lessons learned.

Thanks for reading, and if you have any questions or specific things you'd like to see throughout the series, please feel free to comment below or reach out via the contact me page.