ELI5: Why does bathroom sink water seem to taste different than kitchen sink water?

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Measure the temperature difference of the first 20 seconds of water. That can make a huge difference to taste. Ground water is often cooler than the extra house piping needed to reach the bathroom. Aerators often found in bathroom taps to prevent splashing change the taste too (and get gross, they need removing & cleaning). Your kitchen faucet probably cost twice as much as the bathroom fitting, and is more likely to use ceramic valves and noble metals that don’t impart a bad taste. As the most frequently used faucet it will hold fresher water too.


In UK houses of the past, kitchen cold water came direct from the rising main, as we called it. Direct from the water supply coming in from the street. It is almost always running water, on the move, so it’s fresh, not stagnant. The bathroom typically upstairs, would routinely be supplied from a cold water tank, typically in the attic space. This was water that had been standing around for ages, and was not regarded as drinking water. Fine for washing, bathing, flushing, but only suitable for spitting out once you’d brushed your teeth. You may have a similar arrangement, without a description of your plumbing, nobody can say.


Your kitchen sink faucet likely has an aerator and your bathroom tap likely does not. I would imagine the microscopic air bubbles added to the water explain the change in taste.


Short answer, because no legal or regulatory body or plumber is there to make sure your bathroom water is fit to drink from, and in fact the kitchen tap is the only point that you are supposed to get supplied with food-grade water. In the UK the cold kitchen tap (CKT) will tend to be the point of entry into the property, therefore going through the least internal pipework, and will be the designated drinking point. The mains will be cooler and have a higher level of chlorine. The regulations on mains systems are in place to ensure water is transmitted over long distances without losing its wholesomeness. Internal systems may not be to the same standard. Most changes to taste and odour (t&o) will be either plumbing materials imparting a t&o, or will be geosmin. Geosmin is the chemical responsible for earthy/musty/stagnant t&o, also what gives rainfall on a warm summer’s day. It will be a consequence of environmental organisms and fungi that grow in internal pipework- itself due to warming, plumbing materials, and stagnation. Stagnation allows for warming to increase, and for chlorine levels (chlorine being a gas which dissipates over time) to drop. This process of ‘stuff’ growing is called regrowth, because tap water is not sterile, and things and start to grow when given the opportunity. There may also be more active issues such as backflow from appliances. Generally, it is not advisable to drink from non-ckt points as you cannot be certain of its parameters. Water is (in the UK at least) designated as a food product FROM THE COLD KITCHEN TAP- once it is not from the CKT it is then subject to internal systems and will carry with it the assurances that it would otherwise. It would not be anyone’s regulatory or legal responsibility, for example, to ensure that water is wholesome and fit to drink. That means internal plumbing is designed to follow that, too. Walk further to the kitchen, and run water till it’s cool(er).


Set up a blind taste test. Maybe it’s psychological?