Hot black water coming out of bath tap in newly refurbished. Bathroom

[Bones66]

Hi, I hope someone can help. I’m hoping this isn’t a permanent problem. We’ve converted a gravity vented hot water system, into an unvented indirect hot water system to improve pressure in the house.
The previous cylinders are in the loft now they’re in the garage next to the boiler. We repurposed the flow pipe that’s made of 22 mm copper the previously led from the boiler to the loft and used the section from this to supply the hot water to the house. The problem is that when it flows through the large bath tap black bits come out everything is new apart from the flow section of the copper pipe it seem to have stopped from using the shower and base alone, but when you use the bath tap it restart. I think it’s residue within the closed flow return system within the pipes. it was doing the same in the shower and basin initially, but running them seem to clear it. The bath is being a bit more stubborn. The flow isn’t continuously black. It’s just intermittently black every time you switch off the tap and then restart it the first few seconds of black, and then a minute or so later, a big black gush and splutter

Does anyone know does this clear itself?
Is there something I can use to clean it?
Any suggestions please .

 

[Ben-gee]

If it was the expansion pipe from the old boiler to the feed and expansion tank in the loft, which is what it sounds like, this will have had the central heating water and chemicals in it for years.

Do not use this for domestic hot water - which clowns have done the work?

Re-pipe it with fresh copper pipe.

 

[Bones66]

If it was the expansion pipe from the old boiler to the feed and expansion tank in the loft, which is what it sounds like, this will have had the central heating water and chemicals in it for years.

Do not use this for domestic hot water - which clowns have done the work?

Re-pipe it with fresh copper pipe.

Any other suggestions regarding cleaning it/ flushing it that doesn’t not involve re plumbing house.

It was used so that there was a 22mm supply to main hot water pipe connection in loft.

Would solvent work/ will it clear itself with use. Anyone have experience of this situation.

 

[Ben-gee]

No other suggestion from me , sorry if you don’t like the answer.

 

[Brambles]

Beyond having dirty water passing through to the outlets, debris will probably also have built up in the ceramic valves and (if any) thermostatic shower valve filters. That is the reason your issue is more prominent with the bath tap - the thermostatic shower will probably eventually block.

You should get the installer, or whoever signed off the Unvented Cylinder installation with Building Control to rectify the problem to comply with potable water rules.

Re-piping is the best solution, failing that get the system flushed with acetic or citric acid and then passivated and sterilised.

For a small system, it is probably cheaper to repipe than acid flush.

Note, if you acid flush and then do not passivate the pipework properly pin holes in the pipework will probably start to appear after 12 to 18 months. Acid is more searching than water and will sit within the troughs of the surface roughed pipes slowly reacting with the copper if not passivated.

Check also that if you acid flush the system, the UV cylinder warranty is not impacted

 

[ShaunCorbs]

It’s actually in the water regs not to use previous heating pipes for potable water usage so only option is to re pipe wouldn’t want to be showering in nasty chemicals / old heating water residue

 

[Ben-gee]

I think OP was hoping someone would come along and contradict me.

 

[gpbeck]

No need for 22mm pipe in an unvented system. Just increases dead space losses.

 

[Ben-gee]

I disagree, need 22 if it goes off and feeds multiple showers etc.

 

[gpbeck]

I disagree, need 22 if it goes off and feeds multiple showers etc.

I read this as OP having one bath and one shower.

 

[Ben-gee]

I read this as OP having one bath and one shower.

You’re probably right, I haven’t checked!

 

[Bones66]

No other suggestion from me , sorry if you don’t like the answer.it just seemed off the cuff unneces

 

[Bones66]

That’s fine I just ran full speed in and off for about 20 mins and all good. Just trying to find out from plumbers that f they had come across this. So thanks for your help Ben but it cleared itself without replumbing the house! So idea was sound to use return but hadn’t realised the temporary issue of black water. So if any one else has similar . Don’t replumb , just be patient .

 

[ShaunCorbs]

That’s fine I just ran full speed in and off for about 20 mins and all good. Just trying to find out from plumbers that f they had come across this. So thanks for your help Ben but it cleared itself without replumbing the house! So idea was sound to use return but hadn’t realised the temporary issue of black water. So if any one else has similar . Don’t replumb , just be patient .

Until the water is turned off then back to black bits again

 

[Brambles]

I don’t want to sound to be Jonah, but the black residue is / was probably magnetite, which is potentially toxic to humans. It also causes corrosion of the copper pipe, which increase the Cu concentration in the water.

As an aside repurposing copper gas pipe to potable water can cause similar problems, but with different contaminants.

If you are planning to leave tue installation as is on a potable water system, for peace of mind I would get a sample of the water tested - it costs around £40 ex Vat.

 

[Bones66]

Until the water is turned off then back to black bits again

Then again be patient and will resolve again im sure

 

[Bones66]

I don’t want to sound to be Jonah, but the black residue is / was probably magnetite, which is potentially toxic to humans. It also causes corrosion of the copper pipe, which increase the Cu concentration in the water.

As an aside repurposing copper gas pipe to potable water can cause similar problems, but with different contaminants.

If you are planning to leave tue installation as is on a potable water system, for peace of mind I would get a sample of the water tested - it costs around £40 ex Vat.

Not planning on using for drinking. It’s the hot water supply to house that was repurposed.

 

[Ben-gee]

This is irresponsible behaviour and not something any decent plumber would do.

But crack on, I know you’re very pleased with yourself.

 

[SimonG]

You've fecked up, it's not the way to do it.
End of.