Ask the Architect

How harmful is bleach?


Q. I have a large family — children, parents and grandparents — trying to catch up on cleaning, and I want to ask about using bleach. A plumber friend said we can use bleach, if we dilute it, to wash down appliances and pipes in our kitchen, bathroom and boiler area. The thing that worries me is I read that bleach can cause metal to rust, and don’t want to ruin anything. What do you think? Is it safe to pour down a drain? The drainpipes could hold virus, right?

A. Bleach is extremely corrosive and reactive with metal, as are most concentrated acid and alkali products. Rust, corrosion, oxidation or whatever you call it is caused by the trading of electrons between the metal and the bleach molecules. Bleach is often used to give copper products an aged look, by rubbing the liquid on the copper surface. Even though copper is extremely durable and resistive, it does react to bleach.
There are four grades of copper pipe, based on thickness. Your plumber is right about making sure you dilute the bleach, but there may be an assumption that you have a thicker, or the thickest, grade of tubing. I don’t recommend using bleach if the pipes are copper. Plastic pipes are inert, and don’t react to bleach, but you’ll still want to dilute it.
Pouring bleach down your drain presents more issues than you may realize. It may attack bacteria and viruses, but think of where it ends up. In his recently published book, “Troubled Water: What’s Wrong with What We Drink,” Seth M. Siegel goes into great detail about the consequences of what we put down the drain and how it may affect society as a whole.

We depend on clean water, and can’t survive without it. Many chemicals end up down the drain, and we don’t stop to give it a thought, but we should. Everything from paint to gasoline to pills to hazardous waste from hospitals (which isn’t regulated or monitored at the source) goes down the sink or toilet, and ends up being a real challenge to engineers trying to keep drinking water safe.
Bleach or chlorine comes into contact with bacteria and organic material like food and feces, and breaks down into carcinogenic byproducts such as trihalomethanes. Studies have shown that there is a link between these byproducts and cancer in several species, including humans. So, no, bleach isn’t safe when you consider the overall accumulated effect.
As for metal appliances, the manufacturer’s instructions should be followed. I see only mild soap products recommended in the pamphlets I saved for my appliances — making sure to stay away from electronic parts, of course. Internal components of things like the boiler are also harmed by bleach, since the copper may be thinner. Anti-freeze or glycol is a safer bet, but always consult a manufacturer’s recommendation. Never accept the word of anyone who isn’t an expert before injecting or applying anything, anytime, anywhere. Stay safe!

© 2020 Monte Leeper. Readers are encouraged to send questions to, with “Herald question”  in the subject line, or to Herald Homes, 2 Endo Blvd., Garden City, NY 11530, Attn: Monte Leeper,  architect.