Every Drop Counted: Why Water Metering Matters in the Lab

In a previous Greening the Bench post, Choose Your Level: Reduce Water Waste with the Right Purity, we looked at how matching the water grade to the task at hand can cut your demand several times over. This time we're going one step further back, because before you can reduce what you use, you need to know what you're actually using.

Water is one of the easiest resources in a lab to overlook. It arrives on demand, costing very little per litre, and unless something floods, nobody gives it a second thought. But laboratories typically use three to five times more water than an equivalent area of office space. In most buildings that entire figure sits behind a single meter that is shared with toilets, kitchens and everything else under the roof. If your lab has never seen a number that belongs just to the lab, this one's for you.

You Can't Manage What You Don't Measure

Most labs sit inside a building with one incoming water meter, which is read periodically by the utility company and turned into a single line on a bill that is handled by someone in estates. However, that number doesn't tell us very much that is useful. It can't tell you whether your consumption is increasing, which piece of equipment is responsible, or whether last quarter's spike was a busy run of experiments or a fault that nobody spotted.

Metering can change that conversation entirely. Once you have data for a lab or a single instrument, water stops being a fixed cost of doing science and becomes something you can influence. It also gives you evidence to create a business case for new equipment. For example, a request for a recirculating chiller or an upgraded purification unit, that provides measured litre details, is far more persuasive than one built on good intentions. Finance teams tend to agree a great deal faster when the payback is presented there on the page.

There are two ways to get that data, and they are less a hierarchy than a choice. One is digital sub-metering, which is the gold standard if you can get it. The other is a manual walk round with a measuring cylinder, a stopwatch and a notepad, which costs nothing but an afternoon. Which one is right for you depends on your budget and how much support you have from estates, most labs should simply start with whichever one they can do this month.

The Digital Route: Sub-Metering

Sub-metering means fitting additional meters downstream of the main supply so you can see the consumption for a specific area or piece of kit. It is the difference between knowing that your building used a lot of water and knowing that your autoclave accounted for most of it. If you have the budget and a willing estates team, this is the version worth aiming for, because it carries on measuring long after everyone's enthusiasm for notepads has worn off.

A few practical ways to approach it:

• 🔎 Start with the biggest suspects. Autoclaves, glassware washers, DI purification systems, and any remaining single pass cooling are almost always the largest consumers. Meter those before anything else.

• 🔧 Ask about clamp-on meters. Non invasive ultrasonic meters fit onto existing pipework without cutting into the supply, which makes them far easier to justify and install in a working lab.

• 📊 Get the data logged, not just displayed. A meter you have to walk over to and read by eye will be read twice and then forgotten. Ask for pulse output or a logger that feeds into your building management system.

• 🤝 Talk to estates first. Your facilities team may already have sub-meters installed that nobody in the lab has ever thought to ask about.

The payback is often quicker than people expect. Sub-meters are inexpensive relative to most laboratory equipment. They routinely pay for themselves by exposing one oversized consumer that would otherwise have gone unnoticed for years. However, if the budget isn't there or estates can't get to it this quarter, that is not a reason to wait.

The Manual Route: A Walk Round with a Notepad

The good news is that you won't need to tap into your budget for this method. A water audit is nothing more than a structured walk around your lab, noting every point where water enters or leaves and asking what it is doing there. It takes an afternoon but it almost always shows up something unexpected.

It's worth emphasising that this is method is not a downgrade. A well run manual audit gives you the same thing a sub-meter gives you: a ranked list of what your lab actually uses and the evidence to do something about it. It is less precise, and it won't keep measuring while you sleep, but a rough number you have today is worth a great deal more than a perfect number you're still waiting for.

Work through it in four passes:

• 🚰 List every outlet. Taps, sinks, safety showers, eyewash stations, and the feed to every instrument that takes mains or purified water.

• ⏱️ Measure, don't guess. A measuring cylinder and a stopwatch will give you litres per minute for any tap or outlet. Multiply that by how long it runs each week.

• ❓ Ask whether it needs to run at all. Single pass cooling, water driven vacuum aspirators, and taps left trickling to keep things flowing are the classic offenders.

• 📋 Write it down. Rough numbers on paper beat precise numbers held in someone's head, and they give you a baseline to measure every improvement against.

Whichever route you take, you end up in the same place: a short list of the two or three pieces of equipment responsible for most of your consumption. That means two or three fixes get you most of the saving, which is a far more manageable place to start than trying to change everything at once. And if you go the manual way first, you'll know exactly where a sub-meter would be worth fitting when the budget does appear.

Action of the Week

Pick your single biggest water consumer, most likely the autoclave, the glassware washer or the purification system and find out what it actually uses. If it has a sub-meter then pull a week's worth of readings. If it doesn't, take a measuring jug and a stopwatch to it, work out the litres per minute, and multiply by how long it genuinely runs. Either way, you'll end the week holding a number you didn't have on Monday.

Conclusion: A Step Towards Sustainability

Metering isn't glamorous and on its own it doesn't save a single litre. What it does is turn water from an invisible waste into something you can see, question and improve. It provides you with the numbers and evidence to make the case for every change that follows. Whether that starts with a logged sub-meter or a cylinder and a notepad matters far less than starting at all. You will almost certainly find something worth fixing and every drop you stop wasting is one that costs nothing to treat, pump or heat.

Frequently Asked Questions

What is water sub-metering in a laboratory?

Sub-metering means installing additional water meters downstream of the building's main supply so consumption can be measured for a specific lab or piece of equipment. Instead of one building wide figure on a quarterly bill, you get data you can act on, such as how much water your autoclave, glassware washer or purification system actually uses.

How do I carry out a water audit in my lab?

Walk round and list every point where water enters or leaves the lab, including taps, sinks, safety showers, eyewash stations and instrument feeds. Use a measuring cylinder and a stopwatch to record flow rates, estimate how long each outlet runs per week, and note any use that could be reduced or eliminated. Write the results down so you have a baseline to measure future improvements against.

Do I need a sub-meter to measure my lab's water use?

No. Sub-metering is the gold standard because it measures continuously and takes no effort once installed, but a manual water audit with a measuring cylinder and a stopwatch gives you the same ranked picture of where your water goes. If budget or estates support isn't available, start manually and use what you find to make the case for a sub-meter later.

Is sub-metering worth the cost for a small lab?

Sub-meters are inexpensive compared with most laboratory equipment, and clamp-on ultrasonic models can be fitted to existing pipework without shutting down the supply. They typically pay for themselves by identifying a single oversized consumer, and the consumption data also strengthens the business case for larger investments such as recirculating chillers.