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Comment by instagib | Hacker News Reader

Why you should drain your hot water heater regularly and not use hot water for drinking:

https://blogs.edf.org/health/2018/02/26/lead-hot-water-issue...

They’re lead traps.

This remarkably old advice from a time before modern water treatment, sacrificial anodes, and automated temperature control is also why so many recipes instruct to "fill a pot with cold water" before it's boiled.

Although, seeing the inside of an old water heater is all anyone would need to convince them to leave the hot water for washing.

>Although, seeing the inside of an old water heater is all anyone would need to convince them to leave the hot water for washing.

You're talking about all the mineral sediment gunk that accumulates in them? But that's stuff that was in the cold water supply to the water heater but not in the hot water it emitted. It's evidence of its cleaning action.

And you dont want it to clean the seals of pipes, that contain lead. Lead in pipes normally gets a oxide layer that unless disturbed it usually safe, heat disturbs these and causes said problem. Is it realistic to remove every pipe at once? No but they will work on it probably over 10-20 years, since as long as they don't add oxide inhibitors/removers (mostly what caused the flint disaster) or add heat, it is relatively safe.

I think the point is that a cold water line is easily flushed before use, and it's less likely to breed or incubate biologics.

I wouldn't call water standing in accumulated scale and sediment "clean" any more than I'd prefer to drink from a stagnant pool than a stream!

There are places where the hot water is in an open (!) container in the attic and it could have dead rodents, etc. in it. Ireland, for one - which is part of the persistence of separate hot/cold taps in bathrooms.

Hot water is ~never in an open tank. You’re thinking of cold water tanks; historically these were often open, in Ireland and the UK, though this isn’t allowed under modern building regs. However, the water for the hot water tank usually came from the cold water tank, where present, so you have much the same concern. (There are other concerns with hot water tanks, particularly Legionaries Disease, so even if the cold supply is clean the hot may not be.) This is why water from bathroom taps etc isn’t considered drinkable in countries where this is common.

> which is part of the persistence of separate hot/cold taps in bathrooms.

This was a separate but related issue; for a long time plumbing regs required this due to concerns about the possibility of hot water (considered unsafe due to the above) being forced back into the public cold water system. This isn’t possible with modern mixer taps.

I think you might be thinking of the cold water tank in the attic that was historically used to feed decent cold water pressure to the upstairs taps only.

This is why I was told to never drink out of the taps upstairs as a kid. Think these up much rarer these days.

Hot water is always stored in an insulated hotwater cylinder in the UK, not open.

Yes, that's called a header tank. It's common throughout the UK too. It means low water pressure, especially upstairs. The actual hot water is still in an insulated tank within the house. The header tank holds cold water. Most new installations are unvented systems with no header tank, but this comes with its own tradeoffs.

The hot/cold tap thing is funny. We were just taught not to drink from the bathroom tap at all. It still seems gross to me when people do or like in hotels where you have to.

The header tank is to maintain pressurisation in the radiator heating system; modern "combi" boilers don't need a header tank.

Given that many people leave their plumbing/water system in their homes be just the way it is for decades, it's still wise advice.

Anecdotally, many homeowners are unaware of the existence of the sacrificial anode, and suffer premature water heater failure as a result.

Also anecdotally, some water heater replacement specialist contractors take every precaution to keep customers ignorant on this: No post-mortem examination, no mention of the issue, withholding of the printed manual accompanying the new replacement.

To replace the sacrificial anode on my water heater you need to:

1. Dig the plug bolt out from the spray foam insulation with some tiny picks. 2. Get a breaker bar to get enough torque to unseat the nut. 3. Strap the tank to a wall to avoid it moving when using the breaker bar.

The manufacturers don't want you replacing them either. It took over an hour to do something that in theory could take less than 5 minutes.

That said, if you have an non-heat pump electric water heater like mine you're probably better of letting it die and replacing it with a heat pump based model.

Lol, imagining this post-mortem examination cracked me up-- CSI's Bradford White division.

Most homeowners should not be messing with their own plumbing besides fixtures, the commentary on this thread should be more than enough evidence enough for that.

We have a hot water dispenser in one of our kitchen sink popouts; it's tremendously convenient. It's an on-demand heater that makes 82C instantly for tea.

If it’s a lead trap… wouldn’t that mean the water that comes out has less lead in it than the water that goes in? Assuming the water going into the heater is the same as the water coming out of your cold tap.

No, the article states that lead particles from upstream get trapped inside the water heater, which then gradually dissolve, especially when left stagnant overnight.

Right but all those particles just end up in your glass in the cold water supply right? Better they get trapped in heater.

Whether or not it's a good idea would really depend on what percentage of hot versus cold water ends up consumed (versus used for non-consumption purposes). Over the lifetime of the undissolved lead accumulation.

I believe elemental lead is not terrible when ingested, but lead ions are much worse.

Yeah, metallic lead is pretty safe to handle overall, as long as you don't inhale the dust. I wouldn't want to go trying to ingest it, but the amount of incidental exposure you'd get from handling, say, a lead brick at room temperature, is not much of a worry. Wash your hands after handling it, wear proper PPE, and you should be fine.

Edit: this isn't counting stuff like using lead solder. In that case, ventilate the crap out of your work area (preferably doing the work under a hood), wear PPE, and clean any equipment used.

Leaded solder is no more dangerous than lead bricks. The lead never vaporizes (look up the boiling point of lead if you don't believe me), so the same hazards of skin contact and lead dust are the relevant ones. And lead dust is less of a problem for solder because of the alloys used being a lot less prone to making dust than lead bricks (source: extensive personal experience with both).

The fluxes used in solder are far more dangerous than any lead.

However, carefully washing one's hands only goes so far. Your work area will still be covered in small amounts of lead residue just from all the transfer via tools and fingertips. It is very reasonable to avoid leaded solder entirely these days in favor of newer alloys like SN100C, which have performance very close to Sn63Pb37 (though not the same).

I’ve switched to lead-free solders for all new work, but still do any repair/rework of old products with leaded solder as I’ve never found a lead-free solder that works well (plus, I’ve now got 5 lifetimes’ worth of leaded solder supplies).

Have you found any that work well in repairs/cross-contamination cases? I suspect a lot of the early complaints about lead-free solder being a dire problem functionally were from people using the wrong temp or cross-contaminated tools. (I use a cheaper segregated station for leaded as I got tired of changing tips on the nicer station.)

...honestly we play pretty fast and loose with mixing alloys around here. We really shouldn't since it can be very bad, as you know.

The three RoHS alloys I have experience with are SAC305 (blech, no idea why people tolerate this stuff), SN100C (seems to be great on new assemblies, never much tried mixing it), and REL22 from AIM (this is on our "high strength" spool holder, next to the Sn62Pb36Ag2 silver solder, so people tend to graduate toward it for no better reason) which seems to do pretty well in typical lab conditions after being used to rework either SAC305 or SnPb joints. We don't do real testing around here.

When I am knowingly mixing alloys I will try to clear or flood the joint or both (remove as much old solder as possible with braid, or add new solder in excess). We are pretty good around here about using Way Too Much flux, which is of course the correct amount. This might help. Either way we seem to do okay for this light use.

“The flushing helped significantly in almost every case. Among water heaters where water levels first tested above 50 ppb, flushing dropped the lead levels on average from 456 ppb to 20 ppb”

They took samples from the tank as I understand before and after flushing. If it’s in the sample some of it presumably goes to the water you use.

Right so the hot water tank was trapping lead that, in your cold supply, just passed right through to your faucet.

All that extra lead in the tank didn’t go to a faucet. Seems better.

Of course, it's complicated because the pre-dissolved lead and lead that's formed into salts, etc, is more bioavailable and less likely to pass through you.

Presumably the water heater reaches equilibrium and doesn't remove lead forever-- you get equal rates of lead in and lead out. But the water heater may be making the lead more bioavailable.

Perhaps. Or perhaps hot water picks up more leas from copper pipe solder out whatever downstream.

That’s why this is a really dumb testing method considering a good one (just testing at the faucet) would have been as easy to do.

Testing at the faucet is definitely going to end up identical in concentration (plus whatever it picks up in pipes in the house), but not necessarily bioavailability.

I can’t find anything indicating there’s any difference in bioavailability between hot and cold water, or that it’s a concern at all.

I’d just assume whichever has less lead in it is what I’d rather drink. If the hot water tank is removing lead from the supply and trapping it, I think I’d rather use it for cooking. (Of course I’m not trying to drink warm water out of the tap in any case. )

And in any case what this study is measuring seems to have little relation to what you actually want you know. But I’d guess you’re right, the hot water tank is probably removing some lead (hence the higher concentration) but not enough to matter much.

I strongly suspect the people who say you shouldn’t drink hot water are just parroting something that may be entirely mumbo jumbo, or may be true in some instances for homes with older plumbing but not anymore.

I’ve replaced all the plumbing between the street and my kitchen with Pex so there’s no solder after the water heater. (Perhaps hot water does dissolve more lead from that, though I still have a hard time believing it is significant.)

> I can’t find anything indicating there’s any difference in bioavailability between hot and cold water, or that it’s a concern at all.

Bioavailability of lead salts (like that form when you have a lot of hot water, metallic lead, and other contaminants in a tank for a long time) is higher than of metallic lead.

Similarly, bioavailability of dissolved lead is higher than that of metallic lead particulate. The mechanism we're discussing is metallic lead particulate sitting in water heaters and dissolving.

> I strongly suspect the people who say you shouldn’t drink hot water are just parroting something that may be entirely mumbo jumbo, or may be true in some instances for homes with older plumbing but not anymore.

I suspect the people who say you shouldn't drink hot water have looked at the grody water that comes out when you drain a heater that's sat for a long time and see all the sediment and yuckies that accumulate at the bottom.

I suspect so too and again, their thinking is obviously incorrect. Those sediments and yuckies were all taken out of the hot water supply, but passed right through to the faucet on the cold side.

Every time I drain my water heater, I dumped a bunch of sediment and yuckies down the drain that otherwise would have been in me, if I were drinking from the hot side rather than the cold.

The logic you’re describing is like looking at a gross filter you’re replacing and saying “look at all this junk in the filter, I’m never filtering my drinking water again!”

Filters look gross when you replace them for the exact same reason that hot water tank is full of sediment. It removed them.

> I suspect so too and again, their thinking is obviously incorrect.

That crap usually sits in the bottom of the water heater but it can become less safe with time (e.g. forming lead salts or dissolving lead, as mentioned, or grow legionella cultures). It can also get stirred up and you can get a whole bunch more of it all at once.

It also doesn't all come from the input supply; a lot of it comes from the hot water heater itself corroding over time.

This is a really stupid testing method. They should have tested both water supplies at the faucet. This does seem to indicate the hot water tank is removing lead from the water and thus you would be better drinking it than cold unless something is going on between the heater and your faucet.

drinking hot tap water is really dumb considering this and also legionnaire's disease potential

Other way around. This would indicate cold water has more lead.

Also, Legionnaires isn’t a risk from your water heater.

it is if you don't turn the temperature up high enough.

I was always taught to use cold water for anything to do with food. Never thought of lead.

Water that's been sitting in a heater tank is oxygen-deprived and tastes dull when you use it for food preparation. That's the main reason to use aerated cold water instead of water from the hot-water system.

Probably because hot water is stored and if it happens to go below a certain temperature bacteria can multiply

In some houses, the hot water is fed by an open header tank in the ceiling. Whatever dust, dead mice or bird poos fall into that, can contaminate the tap water. I went off drinking hot water as a kid after seeing the deep layer of fine dust built up in the bottom of it.

As pointed out in a different comment thread here, that’s a header tank which was used in older, multi-level buildings where city water pressure was not adequate for the rise to upper floors. Builders would set up a tank that slowly filled using the lower pressure and could act as a sort of mini water tower for the building. This did not contain hot water, but there is a chance a hot water tank was using this supply.

Where I lived, the cold water was at much higher pressure than hot. I assumed it was common for cold to be mains pressure and hot to be from a header tank when present. Maybe it was an unusual case of retrofitted hot water (house was likely built before the invention of hot water).

Unless you have a tankless water heater and no lead pipes in your house, in which case it’s fine to use the hot water from the tankless water heater for food / coffee / tea. At least that’s my understanding.

That's my understanding also. I only do it if I was already using hot water recently though. It seems pretty wasteful to pour all of that perfectly good cold water down the drain while I wait for the hot stuff to get to the faucet.

I have a tankless water heater. Does anyone know how accurate these things are? https://www.amazon.com/Safe-Home-LEAD-Drinking-Water/dp/B091... I'm down to do some weekend science.

I have a tankless, too, and after reading the article and these comments had the same thoughts...

Water sits in the pipes so I would still run it and still use cold water.

Most dishwashers are connected to hot water. Some higher end dishwashers can work with cold water, but the cheaper ones don’t. Does this mean using a dishwasher is a problem as well?

This must be a US-centric thing, having had many dishwashers in my time and having never seen one with anything other than a cold water inlet.

I assume this is related to the availability of 230v/15A for the heater element.

If you have hot water, why wouldn't you use that for the water connection?

My dishwasher has a heating element, but the colder the water is, the more it has to work.

So if it's cheaper to use gas-powered hot water from the boiler than to heat it electrically, why wouldn't you? And it's there in the kitchen right next to the sink which has hot water available anyways, so it's kind of a no-brainer.

Yes, I'm in the US -- you can see on a kind of average dishwasher installation manual [1], it specifically instructs you to connect it to a hot water line.

[1] https://www.whirlpool.com/content/dam/global/documents/20101...

My dishwasher uses sufficiently little water that it would get mostly cold water from the hot water pipe.

Yeah, the standard advice is actually to run your kitchen faucet on hot until you get hot water, before you start the dishwasher.

I'm always rinsing off the bigger gunks of food with hot water anyways as I load the dishwasher, so it's hot already.

At the end of the day it doesn't matter that much. The main point is just, if you have hot water available, it's hard to see why you wouldn't take advantage of that.

I’d assume that wasting a lot of hot water before running the dishwasher negates any price benefits from heating the water with gas instead of electricity. Not to mention the CO2.

> If you have hot water, why wouldn't you use that for the water connection?

Two protein related reasons: hot water can denature detergent enzymes making them less effective, and hot water can cause food proteins on the dishes to harden and set.

European manufacturers claim that detergents work better when starting the program with cold water, and recommend doing so. The situation might be different in the US, where using the hot water seems to be the norm.

Must be. I'd say most dishwashers are connected to the mains supply and not pre heated.

Probably not. Most of the water runs off the dishes. A very thin film remains that evaporates in the dry cycle, and even at that a lot of it will bead up and run off completely.

I have found that new dishwashers with good eco ratings leave easily detectable amounts of soap on the dishes. Even apart from any health impact, I make it a point to never use them on their default eco programming, but switch to sth that uses more water. I want my dishes clean, that includes soap residue.

I got rid of a perfectly fine 35 yo dishwasher that cleaned fine even without soap, due to heat and water use. I got rid of it because it was loud, but I always wondered if running it without soap was perhaps not as eco friendly as a modern washine using less heat and water.

Use less soap. I use about half as much and the dishes come out fine. I've had better luck with liquid based soaps too as they mix immediately with the water.

You cut those tablets up?

I don't use those, I use liquid dishwashing gel.

Sounds like you're probably using too much detergent.

There's only tablets, how can you use less? Even those that they recommend have this.

Buy powder or liquid instead?

I use either Cascade powder or the Walmart brand equivalent and only put a teaspoon or so of powder in the cup per load and a few dozen granules of powder on the door for the prewash.

The tablets are popular but at least here you can still get liquid or powder detergent for automatic dishwashers.

Havent seen those in over a decade.

What country do you live in?

Does a tankless/instant water heater avoid this problem?

I don't follow. My hot water is heated up about 60cm before the tap, as it runs through. Is that a regional thing? Are you saying that you're keeping a large quantity of water at temperature at all times just in case someone might need it later? Wouldn't that be super inefficient energy-wise?

This is the standard North American approach, we have large insulated tanks that hold water at generally 38-48 degrees Celsius. My home uses a 40 gallon "water heater" using natural gas with an always burning pilot light. It's possible to "run out of hot water" as a result.

The common statistics I've heard is 30% of household energy usage goes to keeping the hot water heater at temp. How much of your power usage is water heating?

Looked at my natural gas usage. In the summer it only used for water heating/keeping it hot at 10 therms/month. Total annual gas usage is 700+ therms. 12*10/700 = 17%. And this includes both heating and keeping it hot.

This site [1] quotes 0.0113 therms to heat a gallon of water. 120 therms / 0.0113 / 365 = 29 gals of hot water per day. This place [2] estimates 41 gallons of hot water per day used during peak demand. My estimate is that we use more for showers, less for washers/dishwashers, same for faucets. Looks like I would spend all of my BTUs on heating these 29 gals of water every day. Most likely close to single digits %% for keeping it hot.

[1]https://webbsupplycompany.com/scalesafe/what-does-it-cost-to...

[2]https://michaelandson.com/blog/what-size-water-heater-do-i-n...

Does this mean I shouldn't be doing my dishes with hot water?

I really doubt any relevant amounts remain on the cleaned dishes.

If you drink the dish water OTOH...

I assume if you have a newer house with PVC or PEX piping, this is not a concern.

Should we worry about plastics instead?

Almost certainly, though most of the problematic plasticizers (anecdotally) probably work themselves out in the first couple years. We likely won't see any real studies on it for awhile though, but [https://www.sciencedirect.com/science/article/abs/pii/S00489...] is concerning.

"In the US, PEX pipe manufacturers often request a pipe to be certified in accordance with the NSF International/ANSI 61 Standard leaching procedure (NSF International, 1988). However, the results are not made public and the water that contacts the pipe for its first 90 days is discarded and not tested. Therefore, there is a general lack of available data to be used for an LCA on US PEX pipe products."

Water in plastic pipes is pretty stanky at first, especially the first couple months/weeks.

PEX has issues with permeability - it's highly oxygen and chemical permeable. Also contaminants from manufacture working themselves out.

PVC has a lot of plasticizers and stabilizers, and warmer temps make it leach faster. Many of them endocrine disruptors.

That said, no such thing as a free lunch. And as long as the water is kept moving, chances are it's fine after awhile. Avoid the 'stanky water fountain' effect by letting the water run a bit before drinking/using it if you're worried.

> Water in plastic pipes is pretty stanky at first, especially the first couple months/weeks.

This is mostly from the glue used at the pipe joints, which has a lot of volatile components.

unfortunately not, the pipes themselves are also an issue. PEX doesn’t use any glue, and all 62 distinct chemical compounds identified in that paper I linked came straight from the pipes themselves.

PVC is even worse in my experience.

PEX (and polyethylene in general) is one of the least concerning plastics, it’s not worth worrying about on that front. (I wouldn’t want to drink out of PVC though since it often contains phthalates as a plasticiser).

Rigid PVC has few if any plasticizers. (This makes sense: it isn't very plastic!) This is the type usually used for water pipe, at least around here. It's probably not very dangerous.

Flexible PVC is nasty.

I remember that one of the plumbers or house inspectors recommended plastic pipes to us and I thought the same thing: lead solder or plastic leaching into the water.

this is more about the distribution lines running to houses than the plumbing in the house.

There are no safe levels of lead exposure and there plenty of homes with lead piping as well as lead service lines: https://www.nrdc.org/resources/lead-pipes-are-widespread-and...

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