Sink water on trains

[Gathursty]

A quick question.

The water that comes out of the tap in toilets on trains is labelled not drinkable so it's not from the mains. Where does the water come from then?

 

[Carlisle]

It usually does come from the mains but it’s stored in tanks onboard the train that aren’t routinely sterilised so unsuitable for drinking .

 

[The exile]

It usually does come from the mains but it’s stored in tanks onboard the train that aren’t routinely sterilised so unsuitable for drinking .

It’s not that long since the only tap in many houses that was truly safe to drink from was the kitchen tap.

 

[Big Jumby 74]

It’s not that long since the only tap in many houses that was truly safe to drink from was the kitchen tap

Quite so, as that was/is directly connected to the mains, where as those in the bathroom are fed from the tank in the loft (in my case) so will be less fresh. Ok for brushing one's teeth/washing, but not recommended for drinking.

 

[Ashley Hill]

It’s not that long since the only tap in many houses that was truly safe to drink from was the kitchen tap.

True, we had a tank in the roof until the mid 1990s.

Also the pipes used for filling coach toilet tanks were not sterilized aand often lay around on the floor when not used. Buffet cars were in my experience were filled using dedicated pipes.

 

[BurningFeetMan]

A quick question.

The water that comes out of the tap in toilets on trains is labelled not drinkable so it's not from the mains. Where does the water come from then?

In our case it does come from a hosepipe, but i certainly wouldn't drink from it.

The water is treated with a chemical to prevent legionella which makes it unsuitable to drink.

The storage method of the hoses used to fill the tanks would make it unsuitable to drink.

The tanks are not routinely (or ever?) cleaned internally.

Please don't drink it.

 

[dgl]

Iirc the hoses that were at Weymouth Station (or still are?) had the ends kept in a bucket of solution, obviously to keep them sanitary, but I can't remember what the chemical solution was.

 

[yorksrob]

It’s not that long since the only tap in many houses that was truly safe to drink from was the kitchen tap.

I wasn't aware that that wasn't still the case !

 

[cool110]

I wasn't aware that that wasn't still the case !

Started to change from the 90s when unvented hot water cylinders made the cold water tank obsolete. Then with combi boilers not having any tanks even the hot water is drinkable, leading to mixer taps becoming more commonplace.

 

[yorksrob]

Started to change from the 90s when unvented hot water cylinders made the cold water tank obsolete. Then with combi boilers not having any tanks even the hot water is drinkable, leading to mixer taps becoming more commonplace.

Thanks - that's interesting to know !

 

[Meole]

Cold water tanks still exist in some older houses, they can be uncovered up in the loft too.

 

[Gloster]

For many years a lot of the water pipes on stations and in carriage sidings that were used to fill coach water tanks or the bowsers used to fill them were made of lead. Some probably still are.

 

[AndrewE]

For many years a lot of the water pipes on stations and in carriage sidings that were used to fill coach water tanks or the bowsers used to fill them were made of lead. Some probably still are.

I'm surprised to read that, I would have put my money on galvanised iron/steel pipes. And a lot of surviving older cast iron pipes too...

 

[Gloster]

I'm surprised to read that, I would have put my money on galvanised iron/steel pipes. And a lot of surviving older cast iron pipes too...

There was no doubt a mixture of different types, but if some could be lead, then there had to be a blanket ban. I think it was mainly the smaller pipes at the last stage of the supply to the flexible pipes that were most likely to be lead. Lead wasn’t banned in water pipes until 1970 and that was only for new installations.

 

[saismee]

For many years a lot of the water pipes on stations and in carriage sidings that were used to fill coach water tanks or the bowsers used to fill them were made of lead. Some probably still are.

A lot of old lead pipes are safe to drink from due to limescale build up, though that doesn't mean there isn't another reason the water is unsafe.

 

[BurningFeetMan]

The water is dosed with hydrogen peroxide.

 

[AndrewE]

The water is dosed with hydrogen peroxide.

Which water? Mains water used to be treated with slaked lime (if needed) to keep it alkaline and not plumbo-solvent. Nowadays they have realised that phosphoric acid passivates the inside of lead pipes so the hassle of getting lime to dissolve in water has been dropped. It's a lot cheaper to blend in liquid acid than it is to try to get lime to dissolve. Wikipedia used to say it was the dominant UK use of phosphoric acid but I think that has been massaged away. https://thewaterprofessor.com/blogs/articles/orthophosphate-in-water says something similar...

Lots of gland nuts on stop-cocks etc which used to be sealed by lime-scale are now weeping because the acid supply is etching out the lime!

It makes a nonsense of the 1970s prohibition of phosphates in washing powders (although some still say "contains no phosphates") and I imagine it is why sewage works effluent is such a problem enriching lakes and rivers.

 

[BurningFeetMan]

Which water?

The water used to fill the tanks on our trains, used for flushing and hand washing, is dosed with hydrogen peroxide.

 

[AndrewE]

There was no doubt a mixture of different types, but if some could be lead, then there had to be a blanket ban. I think it was mainly the smaller pipes at the last stage of the supply to the flexible pipes that were most likely to be lead. Lead wasn’t banned in water pipes until 1970 and that was only for new installations.

I don't think so, water has to be non plumbo-solvent by law. Restaurant car water had to be supplied from trusted sources but the really critical bit was the connections to the cars in platforms and sidings. There was a strict protocol on keeping the hose ends in jerry-cans dosed with chlorine - ordinary toilet-flushing and hand-washing water was supplied by hoses which were just dropped in the sewage-contaminated 6-foot.

One of the jobs in my lab (and all the others) was going round carriage sidings and stations (like New St) where ResCars were tanked and checking all the supply points for hoses properly parked and the presence of free chlorine in the water they were in- besides boarding the trains and taking samples from the taps in them that were used for drinking water.

== Doublepost prevention - post automatically merged: 22 Jul 2026 ==

The water used to fill the tanks on our trains, used for flushing and hand washing, is dosed with hydrogen peroxide.

I suspect that will be in addition, to control the Legionella risk from water sprayed from taps rather than any lead or "food poisoning" risks.

 

[BurningFeetMan]

I suspect that will be in addition, to control the Legionella risk from water sprayed from taps rather than any lead or "food poisoning" risks.

Yes, for Legionella, see my previous post

 

[Gloster]

My experience is from the late 1970s and early 1980s, and I expect that it was a case of playing safe once the dangers of lead were known, combined with the railway’s habit of bringing in a rule and not relaxing it until there was absolute certainty that it was safe. This would have been combined with the way that the railway did not always have a clear idea of what the various pipes were made from: it was difficult enough to know where the pipes where and they weren’t going to dig down to find out.

 

[AndrewE]

Yes, for Legionella, see my previous post

i don't think you have mentioned Legionella ( Sorry, I have just gone back through the thread to post#6. Legionella isn't a risk from consumption, but this thread is about why tap water on trains isn't safe to drink. Bugs grow in warm plastic tanks, especially if not from a sterile supply and will cause tummy bugs - and will probably be a Legionella risk as well if inhaled.

== Doublepost prevention - post automatically merged: 22 Jul 2026 ==

My experience is from the late 1970s and early 1980s, and I expect that it was a case of playing safe once the dangers of lead were known, combined with the railway’s habit of bringing in a rule and not relaxing it until there was absolute certainty that it was safe. This would have been combined with the way that the railway did not always have a clear idea of what the various pipes were made from: it was difficult enough to know where the pipes where and they weren’t going to dig down to find out.

my experience is from working in the lab with the lead - senior - chemist for water supply. (Our boss called him the best chemist on the railway.) I still don't think lead - Pb - has anything to do with this at all. It is about potable (bug-free) water.

 

[sharpener]

Mains water used to be treated with slaked lime (if needed) to keep it alkaline and not plumbo-solvent. Nowadays they have realised that phosphoric acid passivates the inside of lead pipes so the hassle of getting lime to dissolve in water has been dropped.

Very dependent on where you are in the British Isles.

Non-mains water supplies in moorland areas are so aggressive that you need DZR (dezincification-resistant) brass or gunmetal fittings.
Cambridge water from boreholes in chalk is so alkaline it is quite safe in lead pipes, nevertheless they will bring in a new plastic main under their scheme to eliminate all lead pipework (have had this done). The only effect of the phosphate dosing is the scum on tea and coffee, or so I was once told at a conference.
SWW from the Avon Dam on Dartmoor is treated with sodium hydroxide to raise its pH.
Harvested rainwater is naturally pH 5.3 from the dissolved CO2, and try as much as we can we have not found a reliable way of raising it above 6.5 even dosing with sodium bicarbonate (not wanting to handle NaOH).

 

[Steve Harris]

i don't think you have mentioned Legionella ( Sorry, I have just gone back through the thread to post#6. Legionella isn't a risk from consumption, but this thread is about why tap water on trains isn't safe to drink. Bugs grow in warm plastic tanks, especially if not from a sterile supply and will cause tummy bugs - and will probably be a Legionella risk as well if inhaled.

== Doublepost prevention - post automatically merged: 22 Jul 2026 ==


my experience is from working in the lab with the lead - senior - chemist for water supply. (Our boss called him the best chemist on the railway.) I still don't think lead - Pb - has anything to do with this at all. It is about potable (bug-free) water.

Correct. Potable water is water suitable for drinking even if it is stored in a tank in a train, or aircraft (and every piece of infrastructure which delivers potable water is sterilised and flushed on a regular basis and records are kept). Whereas water is just water and may or may not be drinkable.

I used to know someone who sterilised potable water infrastructure and apparently there was* no specification laid down that water supplied by water companies shouldn't contain any legionella bacteria.

* I have no idea if that is still the case or not.

 

[AndrewE]

Correct. Potable water is water suitable for drinking even if it is stored in a tank in a train, or aircraft (and every piece of infrastructure which delivers potable water is sterilised and flushed on a regular basis and records are kept). Whereas water is just water and may or may not be drinkable.

I used to know someone who sterilised potable water infrastructure and apparently there was* no specification laid down that water supplied by water companies shouldn't contain any legionella bacteria.

* I have no idea if that is still the case or not.

There probably isn't because Legionella is ubiquitous. The risk comes when you have some sort of nutrient in the water (such as stuff which has fallen into an uncovered header tank) and then the water left stagnant somewhere warm like a pipe or shower head in a hotel.

 

[sharpener]

There probably isn't because Legionella is ubiquitous. The risk comes when you have some sort of nutrient in the water (such as stuff which has fallen into an uncovered header tank) and then the water left stagnant somewhere warm like a pipe or shower head in a hotel.

This has been much discussed in heat pump circles bc lower HW temperatures increase the theoretical risk. Consensus is that it is unlikely to be a problem in domestic hw tanks with high turnover (for ppl with unimpaired immune systems anyway). This article is an oft-quoted source. Institutional settings are the main risk.

 

[AndrewE]

Very dependent on where you are in the British Isles.

Non-mains water supplies in moorland areas are so aggressive that you need DZR (dezincification-resistant) brass or gunmetal fittings.
Cambridge water from boreholes in chalk is so alkaline it is quite safe in lead pipes, nevertheless they will bring in a new plastic main under their scheme to eliminate all lead pipework (have had this done). The only effect of the phosphate dosing is the scum on tea and coffee, or so I was once told at a conference.
SWW from the Avon Dam on Dartmoor is treated with sodium hydroxide to raise its pH.
Harvested rainwater is naturally pH 5.3 from the dissolved CO2, and try as much as we can we have not found a reliable way of raising it above 6.5 even dosing with sodium bicarbonate (not wanting to handle NaOH).

You are right, of course. All these comments about lead should have been prefaced with "in soft-water areas." It's one of those things that's so obvious you can forget to say it.

 

[Gathursty]

Thanks for the replies. You are a very knowledgeable lot!