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What Your Senses Can Tell You About Tap Water Quality

by John Pujol, CEO at Tap Score

We all want our water to be crystal clear and refreshing. Nothing is less welcome than a glass of tap water that is discolored, smells off, or tastes funny. Regardless, it’s a relatively common predicament. But are aesthetic issues indications that a tap water supply is unsafe to drink? Not exactly—and not always. After all, some of the most potentially hazardous water contaminants—like lead, arsenic, and PFAS—cannot be seen, smelled, or tasted. It’s vital for a home inspector to know the difference, and to know when these issues are a sign of something serious. Because water chemistry parameters are always in flux, getting a sense of a property’s water quality takes a little assistance, preferably from a certified laboratory. That’s not to say aesthetic indicators aren’t a helpful way to get insights on water quality issues; they are, as long as you know what to look out for.

Color
The first indicator that something might be the matter with a property’s water supply is a change in the color of the water. Common color changes include reddish-brown or yellow, murky, white or cloudy, blue-green, and occasionally, water with an oily sheen.

The most common culprit is reddish-brown or yellow water. You’ve seen it in the movies to signify dire straits: someone turns on a faucet and ruddy-brown water sputters out. But while iron is the primary reason for reddish-brown water, there’s a little more to it than meets the eye. Iron can get into a water supply for a variety of reasons, and it isn’t always a sign that a building’s pipes are rusted.

Two questions to ask yourself are: first, does the tap water eventually clear up, or does it remain reddish-brown or yellow? Second, and importantly, does the water come from a private well on the property or a water utility?

Tap water that clears up after flowing from the faucet for a while is an indicator of a plumbing issue. This could mean faucets and fixtures, old pipes, or even simply a rusty water heater (only if the hot water comes out discolored). If the property is supplied by a public utility, the utility could be performing maintenance, or they may have recently flushed out their lines.

As for private wells, the iron issue could be more than just piping. Iron is naturally occurring, and a groundwater supply that is rich in iron will lead to iron buildup. It may also foster iron bacteria growth, which can lead to some other undesired aesthetic effects besides yellow-orange water, like yellow slime, black gunk, or even an oily sheen.

It’s important to note, however, that despite how unpleasant a ruddy- brown or yellowish glass of water may look, it isn’t necessarily unsafe to drink or bathe in. The iron itself doesn’t present a health hazard, but there may be other contaminants in the water depending on the source of the iron. A water test will easily clear all this up.

Some quick notes about other instances of discoloration: Murky water is most common in properties with private wells and can indicate an issue with the well’s sediment trap, especially if you can see actual solids floating around in the glass. White or cloudy water is most often a case of suspended solids, or simply air bubbles, particularly if the water clears up after sitting for a while. If copper corrosion has reached a point where the water of the sink and its surroundings are turning blue-green, it is likely unsafe to drink. It’s also time for a costly re-pipe. For private well supplies, algae growth (particularly in the warmer months) can impart a greenish color to water. It can also produce an odor. And with the variety of toxins algae can produce, this situation would also render the water unsafe to drink.

The bottom line: a case of discolored water is not necessarily a health risk, but it is a sign that a few things may need some adjusting or mitigating—from aging plumbing components to bacterial growth. So it’s a very good idea to have a water sample analyzed by a certified laboratory to get the clearest picture of what needs remedying, especially if the property in question is over thirty years old. This is because homes built before the early 1990s are more likely to have aging pipes and components that could negatively affect water quality.

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Odor
After inspecting the color of a glass of tap water, a good sniff is in order. Odor can be tricky because it’s the most immaterial of the three aesthetic concerns. The most pungent of the water-related odors is that familiar stink of rotten eggs, but water can also smell like chlorine or bleach, must, mold, or even fish. It can also smell of petroleum and its byproducts.

The first step is trying to locate the source of the smell. There’s a simple heuristic you can follow using nothing but your nose: Does the smell come from one faucet or all the faucets? If it comes from only one, it will probably go away if you run the tap for a little while, indicating that the problem exists within the faucet in question or the specific pipes that feed that faucet. If the smell comes from all faucets, does it go away if you run the tap for a while or not? The cause of the odor might stem from one of three possibilities:

• The property’s plumbing network (if the smell dissipates after running the faucet)
• The water heater (if the smell only affects hot water)
• An issue with the water source (particularly for private well systems), which merits further investigation. 

If your water smells like rotten eggs, it’s not a cause for alarm, but it is a sign of sulfur-reducing bacteria, which can grow in drains, water heaters and water softeners, and even in wells themselves. It is worth noting that hydrogen sulfide, which is emitted by the sulfur-reducing bacteria, is corrosive to iron, stainless steel, copper, and brass if left unmanaged. Therefore, appraising a rotten egg smell should warrant a water test to get a clearer picture of hydrogen sulfide levels and any contaminants that may have been released by corrosion.

It’s also common to pick up on chlorine or bleach smells, which are often a sign of elevated chlorine levels in a water supply. Chlorine is a common water disinfectant, added to most tap water supplies by water treatment facilities. The scent should disappear if exposed to air for a few minutes, but you might want to investigate further if it doesn’t dissipate or is particularly pungent and the property is on a city water supply.

Moldy, musty, earthy, or fishy smells are typically an issue reserved for water from private wells and are a sign of increased bacterial activity. A shock chlorination regimen along with a flushing of the system—and a checkup on the well’s pressure tanks— should remedy the problem. Oil or petroleum smells should be investigated immediately, especially if there is any heavy industry in the area. There’s nothing you want in your water that smells of gasoline or petroleum byproducts.

Generally, the source of a foul smell is often not the water supply itself but an issue somewhere in the plumbing. If an inspection of the plumbing system doesn’t reveal a source, remember that a water test often will.

Taste
Taste is often the last in line, simply because you’re less likely to take a sip from a glass of water that looks or smells off. But taste can tell you something about water quality. It’s also considered the leading reason people opt to filter their water in the first place. Taste is highly subjective, so take the descriptors with a grain of salt. As with the other two aesthetic concerns, taste doesn’t necessarily reveal whether or not a water supply is compromised. Only a water test can do that. But it can be a clue to issues that might merit investigation before a sale is finalized.

Sometimes water can take on a metallic taste due to elevated concentrations of metals, like iron, zinc, and/or magnesium. These are all relatively common and no cause for alarm. But higher than normal concentrations of metals in water should encourage a closer look at the property’s plumbing situation. Zinc, for example, can enter water through the corrosion of galvanized pipes. Importantly, galvanized pipes that are or were downstream of a lead service line (an issue with older buildings) might have captured toxic lead particles and can leach lead along with its zinc particles. Lead cannot be seen, smelled, or tasted.

As with odor, the taste of chlorine can be a sign of higher than normal levels of chlorine in the water, which is a key part of making sure water remains safe to drink. Some have described water with high TDS (total dissolved solids) levels as bitter or salty. Low TDS is often falsely equated with better water quality—neither high nor low TDS is a sure indicator of water quality, it’s only one parameter among many.

The vast majority of minerals measured by TDS are harmless, in fact. Salty-tasting water is also associated with high chloride and/ or sulfate concentrations, and, while not directly a health concern, elevated chloride and/or sulfate in water should warrant further investigation, particularly for a property with a private well because it could be a sign that runoff—from simple road salts to agricultural and even industrial waste—has entered groundwater supplies.

Lastly, properties with aging PEX, PVC, or another plastic polymer material for piping can lend a plastic-like flavor to tap water. The link between plastic polymers and human health is a complicated one—a subject for a different article. Suffice it to say, as a home inspector, tap water with a plastic flavor definitely deserves attention.

For a home inspector, everything covered above can offer clues as to whether or not the water supply should be tested by a certified lab. Even if there are no sensory traces, it’s always encouraged to include a laboratory water test as a part of any property transfer. It’s also widely recommended to have a water supply tested any time changes to color, smell, or taste occur—particularly for properties with a private well. Sometimes, these indicators can in fact be a sign of something more serious going on. Other times, they really are only aesthetic issues that can be taken care of cost effectively.

Testing provides you with the ability to make decisions tailored to what’s actually in the water. Understanding how to appraise the aesthetics of water quality, and how you should respond to different circumstances, can help make any home inspection that much more thorough.

About Tap Score
Tap Score offers certified laboratory water testing designed to make drinking water analysis easy, reliable, and accessible for homes and businesses. Through mail-to-lab test kits, Tap Score combines the scientific rigor of a world-class laboratory network with a simple, user-friendly process, delivering fast, unbiased results. Each lab report provides clear analysis, expert insights, and personalized recommendations, making Tap Score a trusted choice for safe and informed water quality decisions.

About the Author
John Pujol, CEO of SimpleLab and Tap Score, holds a Master’s Degree in Engineering from UC Berkeley. He is a water quality expert with a background in the commercialization and development of electrochemical arsenic remediation, off-grid water treatment and UV LED technology for pathogen and pharmaceutical inactivation. Visit GoSimpleLab.com to start offering water testing to your clients.

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