Why aren’t taps and pipes filthy on the inside?



So kitchens and bathrooms need cleaned regularly. The moisture and food in these rooms specifically make it easy for pathogens to grow. Plenty of people get mould problems in their homes. Kitchens need cleaned with disinfectant sprays to make them safe to produce food in.

What about the inside of taps though? Depending on the age of your house, the pipes and taps could be decades old, and will have never been cleaned on the inside, yet we don’t think twice about pouring a glass of water. Why is this? How are the insides not full of rust, grime and bacteria?

In: 160

Mold comes from airborne spores. Mold needs air and food to survive. Inside of a water pipe there’s just pressurized water – no air, no food. Plus the water utility puts chlorine in the water so even if a little bug starts getting into the water through a tiny crack in one of the pipes, the chlorine will kill it.

You do get a build up of rust on the inside of cast iron pipes, through a process called tuberculation, but that doesn’t make you sick

The water that flows through fresh water pipes and taps is usually treated and is reasonably clean and free of pathogens.

Most wells tap fossil water from deep underground that is also free of pathogens.

So there’s few molds and bacterial present. The water pressure tends to flush the insides of pipes clean, too.

Finally, many homes use copper pipes, a metal that is naturally anti-microbial and resists corrosion, and brass fittings, an alloy containing copper.
Copper kills most pathogens on contact so they cannot adhere to the walls of the pipe.

There are some modern plastic fresh water pipes (PEX) that can support biofilms, if the water source is contaminated.

Well, they do have some. Most water from a non-well source (city water) has chlorine in it, and another chemical I can’t recall… These help to keep the pipes clean. Used to work in a lab that was experimenting with UV LED’s in faucets that would kill bacteria and such…

Let me introduce you to Legionella. It mostly happens in stagnant warm water (usually underused hot water heaters) but has been known to grow in dead pipes. Think plumbing renovations in which a branch is capped and terminated but not removed at the branch.

Pressure at the termination will keep fresh warm water with bacteria from getting flushed out of the system while still at harmless levels. Kinda rare but there are some cases where a terminated pipe became a cesspool of bacteria which ended up growing into the main branch lines, causing great harm and illness.

Flow and temperature will mostly keep things tolerably clean. I used to do legionella checks on water systems. Stored hot needs to be around 60 degrees C and cold below 20 degrees C. Obviously cold can get warmer if the ground gets warm in summer but those are the recommended safe limits, in the UK at least. If your hot is just on demand, no real worries as long as it gets hot enough. The other hazard is capped off dead legs of pipe, which can become reservoirs of legionella, so they should be cut back. Low use outlets should also be flushed for a few minutes at least weekly.

The other one that causes some concern is pseudomonas aeruginosa, but that’s really more a problem for care facilities with immunocompromised folks. That one lives in the biofilms that can coat pipes so we treat that with chlorine dioxide, the same stuff that the miracle mineral supplement idiots drink.

There’s very little in pipes of treated water for bacteria as far as air and food. There’s also chlorine. But things can grow in them. Plumbing is designed with the assumption that water will be cycling through fairly often and not sitting still long enough to let it grow much. I site I used to work at actually had a design oversight that caused potential dangerous bacteria to grow in the water line. Specifically to an out building at the perimeter (the security checkpoint I worked in often). This happened because that building had a 1/4 mile plumbing run from the main building and used a higher diameter pipe than what was needed to seve 4 toilets and an employee break room that were only used mainly by the 3-5 security personnel stationed in that building. So legionella started to grow in the pipes and we were all warned about it.

chlorine and filtration

regular maintenance of infrastructure

regular monitoring of water quality

Because water runs through them often enough that most things that would start building up get rinsed away pretty quickly. Have you ever taken a dirty dish, put it in the sink, then turned on the water and watched how much of the gunk on the dish gets pushed away immediately, well that’s basically going on inside of the pipe whenever it’s turned on.

[Google tuberculation](https://www.google.com/search?q=tuberculation). The insides of older pipes are nasty. Heck, look at your shower head and you’ll likely see hard water build-up.

As for why we don’t worry about bacteria — Municipal tap water contains low concentrations of chlorine which is a disinfectant that effectively kills waterborne bacteria and pathogens and/or keeps them from replicating in the system. Yes, if you tested your water for bacteria, you’d probably find some, but their concentration is low enough not to be a health concern. Plus, when bacteria of concern are detected in tap water (like e. coli), boil water notices go out.

I purchased a home built in the 80’s where the previous owner replaced the pipe from the meter at the curb to the main inlet near the house with this old stuff called Quest pipe, a precursor to pex pipe. Should I worry more about bacteria? I’ve already had to repair 3 breaks in the line; dig, cut, mend. Would love to replace it with copper but the line runs under a large driveway and I was recently quoted 5 grand for the job.

I have well water, and we’re still using the original well from 1952… It wasn’t shocked properly, or often enough, so we had a very constant flow of algae growing in our pipes and toilets.

We shocked it really well last year… Now it’s a constant stream of dead algae. O.o

Back when I was in high school, we’d come back from summer vacation and the fountain water would run a reddish-brown, presumably from rust in the pipes. But after running it for a minute or less, the water ran clear and would stay that way the rest of the year with normal use. So, I’m thinking not only the chlorinated water helps, but the regular movement of water through the pipes helps to clear any debris that might otherwise have gathered.

Domestically, the ‘end of lines’ in a water systems do need to be flushed periodically to prevent bacteria from growing.

Not trying to be rude in any way, but why do people talk like that? “Bathrooms need cleaned” vs “Bathrooms need to be cleaned” ?

I’ve heard this phrasing so much that I’m sure it’s acceptable but it makes my stomach hurt.

Plummer here. I’m not going to talk on there being bacteria because I know nothing of that but when it comes to rust and build it depends on the type of water pipe. Newer plastic pipe called pex never rusts or grows build up because well it’s plastic. But older galvanized pipe (iron) over decades will build up so much rust you can’t even see light through the other side. Copper pipe is different though it will never rust or accumulate build up no matter how long it’s is there but it busts easily in cold weather. Although copper will build up corrosion on the outside if it is in contact with any wires with electricity or just metal in general. Now sewer pipes are a whole different story and you don’t want me to get into that. It doesn’t affect your health and will never interfere with your water in any way but you just really don’t want to know what I’ve seen