Hot water from the cold tap?

[Gert_Lush]

i know this has been covered in the past, but the thread i read about it, didn't cover my issue.
When i turn the cold tap on after it hasn't been used for an hour or so, and when the CH is on, there is a slug of hot water that comes through for about 15 secs, after which time, it returns to normal temp.
Is this a problem or simply a case of localised heating from the hot pipe somewhere along the way, when the hot and cold pipes are in close proximity?

 

[Slugbabydotcom]

there is a slug

Yes there is and here I am!

Are you using my name in vain


It does seem to be a case of localised heating as you suggest.

You need to get to the bottom of this ASAP due to the risk of legionella

Dont drink water from the affected tap/s without boiling it first!

 

[Gert_Lush]

Cheers slug

But now you have me worried.
i wash my teeth using that water, and sometimes drink from it. The cold water in question comes off the rising main not the tank in the loft, so is their still a risk?

 

[boilerbeasty]

Your cold water pipe may be touching a heating pipe or the hot water pipe, transfering heat. The water probably doesn't sit in the pipes for that long, and doesn't get an opportunity to pick up additional contiminants. Tap water still has some bugs in - perhaps if these were warmed up to just the right temperature they could multiply ? In the case of a big water tank, this is where you have the possibility for contamination and incubation. You're likely to run the tap until its cold, so the level of contaminents would be low even if the warm water had developed something.

I had the same problem in my house where the pipes had been passed through a wall. I located the problem and separated them with some insulation lagging foam to stop them from touching.

 

[Gert_Lush]

I'll sort this as soon as i can.... is their likely to the a 'culprit' location, or is it a case of being brutal with the floor baords?
The second bathroom is affected as well, so the source has to be close to the cylinder before it splits...

 

[Slugbabydotcom]

Don't worry too much the risk is actually quite slim especially if you take precautions but it is nevertheless real and should be attended to.
The temperature in which bacteria proliferate is between about 20ºC and 58ºC. The recommended spacing between hot pipes and a cold water pipe is 50mm.