When Aaron MacDougall opened Broadsheet Coffee Roasters in Cambridge, he quickly learned that you can pick your beans, but you can’t pick your water.

MacDougall sources his coffee beans from all over the world: Columbia, Ethiopia, Uganda, the list goes on.

But the water pumped through his Cambridge pipes is a lot more local. It comes from two reservoirs just west of Boston. And MacDougall is not a fan.

Cambridge is one of the few municipalities in the Boston area that's not part of a regional water system, the Massachusetts Water Resources Authority. The city goes it alone, treating and pumping its own water.

The Cambridge water department says the city’s water is safe and cheaper as a result. But Cambridge water isn’t working for one group of city residents: coffee connoisseurs.

As MacDougall explained, the water “does carry a very distinctive — slightly saline, slightly baking powder-y, baking soda-y — taste.”

It’s not just MacDougall. His machines are not so happy about the tap water, either.

MacDougall said Cambridge has become notorious among high-end coffee machine manufacturers. It’s so bad, he said, that some manufacturers will not honor warranties for products that use Cambridge tap water.

Three Problems For Coffee Connoisseurs

MacDougall is quick to say he wouldn’t consider moving his bustling café. He loves the city of Cambridge and the local clientele. But he is also quick to list off three major concerns about the water’s impact on his coffee.

First, the pH.

The gold standard for brewing a great cup of coffee is water with a neutral pH of seven. But in Cambridge, the pH can be nine or even a bit higher. MacDougall attributed the baking soda-y taste to the elevated pH: “It doesn’t taste great.”

Second, the Total Dissolved Solids, or TDS.

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The latest numbers published by Cambridge puts the TDS count at 469 parts per million — just below what they call the “highest allowed level” of 500. By comparison, water from the MWRA — which supplies to the vast majority of Boston-area cities and towns — is often somewhere between 120 and 140.

“It’s not like floating flotsam and jetsam or anything big. It’s generally the minerals and the calcium and the like in the water,” said MacDougall.

MacDougall said the problem with a high TDS count is that there is so much stuff already dissolved in the water that it can’t effectively highlight the taste of the coffee.

“It generally tastes thin. It can taste overly acidic,” said MacDougall. “It doesn’t have a fullness or sweetness to it.”

Finally, the chloride count.

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This is a problem for MacDougall, largely because it’s a problem for his machines.

Just as MacDougall was opening his café two years ago, “one of the major espresso machine manufactures issued an edict saying, 'If you are going to be buying our equipment and installing it in Cambridge, you need to do something about the chlorides in your water supply. And if you don't achieve a certain chloride count, we are not going to honor the warranties.’”

The problem is that under heat and pressure, chloride becomes acidic and corrosive. This means the equipment doesn’t last as long as it should.

Just like the TDS count, the chloride count in Cambridge is higher than water that comes from MWRA. The MWRA water is 36 parts per million; Cambridge water is 235. The Massachusetts Department of Environmental Protection guideline says to keep it under 250.

“You’re getting pretty close to that line,” said MacDougall.

MacDougall’s Solution

In the basement of Broadsheet Coffee Roasters, there’s a temperature-controlled room full of burlap bags stuffed with coffee beans. And on the other side of the wall, MacDougall has figured out a solution to his water woes.

A quietly buzzing cart filled with cartridges looks like it comes from a chemistry lab. It’s a reverse osmosis system, constantly at work purifying water that goes into Broadsheet’s coffees and teas.

“The pre-filtered water comes in and passes through a reverse osmosis membrane. Basically, the water is separated into a brine,” said MacDougall. “It’s not terribly ecologically friendly, because you are creating wastewater.”

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In the basement of Broadsheet Coffee Roasters is a reverse osmosis system that purifies the water the cafe uses for making coffee. Four gallons of waste water are tossed for every one gallon that is able to be used.
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How much wastewater? In this system, about four gallons are tossed for every one gallon that becomes café au laits, americanos and lattes. MacDougall said this is way better than many reverse osmosis systems.

He estimated that the total cost of the extra water, the machine and the maintenance is up to $10,000 per year. MacDougall is not alone. He said several other coffee shop owners in Cambridge have come up with similar systems.

What Is In The Water?

On the edge of Fresh Pond Reservoir in West Cambridge is the city’s water treatment plant. With high ceilings and bright skylights, the building is filled with buzzing machines that help the water move through the various stages of filtration and disinfection.

Sam Corda is the managing director of Cambridge’s water department. A mechanical engineer by training, he used to work on gas-turbine engines and lithium batteries. He’s been in charge here for nearly 20 years and can easily explain each of MacDougall’s concerns.

“We actually increase the pH to 9 as it leaves the facility,” said Corda. That baking soda-y taste may not be good for coffee, but Corda says the elevated pH is good for our health.

“What that does is it puts a passivation layer on the pipes, so you don’t leach in copper or lead,” said Corda. “We’ve been very successful at reducing the lead, as a matter of fact.”

Corda said the TDS and chloride counts originate at the source of Cambridge’s water.

A little more than a century ago, Corda said Cambridge saw the city was expanding. So, in addition to Fresh Pond Reservoir in Cambridge, they bought two reservoirs west of Boston — Hobbs Reservoir and Stony Brook Reservoir. Water flows from the surrounding area — Lincoln, Lexington, Waltham and Weston — into the reservoirs and through a conduit to Fresh Pond and into this treatment facility.

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The Fresh Pond Reservoir in Cambridge, Mass., is fed by water from Hobbs and Stony Brook Reservoirs that are located along Route 128.
Meredith Nierman WGBH News

“In that journey the water takes, it will collect minerals,” said Corda to explain the TDS count.

Corda said the TDS doesn’t worry him, but he is keeping his eye on the chloride level, which he said is creeping upward.

He attributed the chloride in the water largely to de-icing salt that’s sprayed on the roads in the winter to keep things from getting too slippery.

“Interstate 95 — or the alias Route 128 — goes right through [both] reservoirs,” explained Corda. The salt on the roads finds its way into the environment and dissolves into the water, becoming sodium and chloride.

In a statement, the Massachusetts Department of Transportation (MassDOT) said, “maintaining safe roads while being good environmental stewards is a balance MassDOT strives for.”

At the current level, this is not a health or safety issue, but Corda admitted it isn't great for the high-end coffee machines or hot water heaters. However, he said, that can be fixed by using the proper materials and figuring out the right system.

“There are changes in the water chemistry, and you need to account for that from a design perspective,” said Corda.

The city is also taking action. This summer, they're teaming up with MassDOT and folks at UMass to launch a new study. The goal is to figure out exactly where all the chlorides are coming from.

"We will then work with MassDOT or private entities to develop a strategic plan to reduce the chlorides," said Corda.

In the meantime, John Lienhard V, an MIT professor of water and mechanical engineering, is not worried. “No risk to anyone,” he wrote in an email.

Damon Guterman, a senior analyst in the drinking water program at the Massachusetts Department of Environmental Protection, explained that the 250 parts per million limit for chloride is an "aesthetic limit."

If you go above an aesthetic limit, “it could make the water undesirable to some part of your consumer base and that could be taste, that could be odor, it could be visual, it could be some coloration to the water,” said Guterman. But, he confirmed, it’s not a health concern.

Why doesn't Cambridge just use Massachusetts Water Resources Authority water like everyone else?

First, having your own source is cheaper, said Corda. He estimated it costs about half the price per gallon compared to what everyone else pays.

“The other benefit is [that] the city’s in control of its own destiny,” Corda said. “We can optimize everything to give us way above average water — every day.”

And this is where Cambridge’s water experts and its coffee connoisseurs agree. They both want to optimize everything about their water. But coffee connoisseurs say Corda’s cup of “way above average water” creates a below average cup of cappuccino.

The pump room at the Cambridge Water Department is one part of a vast system for filtering and disinfecting the city's water.
Meredith Nierman WGBH News