"Blocked" hot water pipes

[Rich_W]

All,

Having some trouble with my hot water supply at the moment. I've got a standard hot water tank in an airing cupboard rather than a combi boiler.

When I run the hot tap, hot water comes out for about 30 seconds, but it slows to a trickle and eventually peters out. If I force mains cold water through the hot water pipes (by connecting a washing machine hose to the mains cold and hot water supply), the flow/pressure from the hot water taps is fine (albeit cold!)

At first I thought it was an airlock, and the spluttering from the hot taps seemed to confirm this. However, I've run the cold water through the hot water pipes a couple of times now, and it doesn't seem to have solved the problem (other than temporarily). The fact that cold water pressure is OK, but the hot water isn't, suggests a problem in or around the hot water tank (at least, that's my best guess).

Can anyone offer any other suggestions before I call in someone to look at the hot water system? Looks like my gym membership is going to come in useful for taking showers...

Thanks,
Rich

 

[keego]

Check the outlet on your cold water storage tank is not blocked, sometimes if the lid has not been fitted things like dead birds & rats can cause a blockage.

 

[pannierstan]

Why dont you find the Domestic Hot Water header tank and then check the ball cock.
I think you will find its not filling

Stan

 

[Rich_W]

Why dont you find the Domestic Hot Water header tank and then check the ball cock.
I think you will find its not filling

Stan

Spot on - the ballcock was stuck and quite furred up with limescale. I think I'll get in replaced but in the meantime, my cold water storage tank is filling up nicely.

Thanks for your help - it's good to know there's somewhere you can find answers to random plumbing questions at 10pm on a Sunday night!

 

[Softus]

This doesn't make sense. How can a furred-up float valve on a cold storage cistern cause the hot service to peter out after only 30 seconds?

Were you were running a cold tap at the same time as the hot, or perhaps immediately beforehand?

 

[pannierstan]

What do you mean it doenst make sense. He has confirmed it!

Quiet simple when you have come across it many many times.

Ballcock sticks and only fills very slowly. Depending on time it takes relates to the amount of hot water you get before it runs out.

Stan

 

[sime10]

This doesn't make sense. How can a furred-up float valve on a cold storage cistern cause the hot service to peter out after only 30 seconds?

Were you were running a cold tap at the same time as the hot, or perhaps immediately beforehand?

Me think he means the ballvalve for the cold feed to the cylinder was slow or nearly stopped

 

[Softus]

What do you mean it doenst make sense.

I mean that the facts he has declared don't fit the diagnosis - there's some missing information. I'm asking for clarification because someone else with less knowledge that you might read this and benefit from it. Remember the bigger picture.

He has confirmed it!

Not bleeding yet he hasn't!

Quiet simple when you have come across it many many times.

Ballcock sticks and only fills very slowly. Depending on time it takes relates to the amount of hot water you get before it runs out.

That much is obvious, but are you saying that he has indeed run off a lot of cold water before opening the hot tap for 30 seconds?

All I'm asking for is clarity, and I don't appreciate you treating me like someone who's incapable of understanding - you're teetering on the edge of a gross misjudgment...

 

[sime10]

Looks like my gym membership is going to come in useful for taking showers...

Payment in Kind ?

 

[Rich_W]

Morning all,

Didn't mean to cause such a stir! To be fair, I perhaps didn't give all the information I could - this problem first manifested itself on Thursday last week. By Saturday morning , it seemed like it had been fixed but then the same thing happened yesterday evening.

By way of an explanation of my system - as far as I can tell the only cold water feed from my cold water tank is my power shower. All other cold water is fed from the mains. I assume (you guys will know better than me), that this is the same tank which:

a) fills the hot water storage tank
b) provides the gravity fed pressure to the hot water taps/shower head

When I got in to my loft last night, the tank was pretty much empty. I suspect what had happened is that the use of the power shower had drained the cold water tank and therefore left no pressure to feed the hot water from the hot water tank to the taps/shower.

The ballcock mechanism was stuck in its highest position, stopping the tank from filling up. I moved this down to allow the water to flow in and then waited for the tank to fill up completely - I checked that the ballcock did its job properly by stopping the water supply to the tank. Once full, I had a (lovely) shower, and then checked back in my loft to hear the tank filling again.

This morning, there was hot water from the sink tap for me to shave, and the shower was working perfectly. My pregnant wife was very pleased with the situation!

Hope this gives everyone a bit more clarity around the situation - I'm happy to expand on anything if it makes things clearer. As Softus points out, it's worth giving a fuller picture if it helps someone else who searches for this topic.

Thanks again to all.

Rich

 

[HarrogateGas]

Well done Pannierstan. looks like whatever peoples opnions are on this, yours are the right ones to follow!!

Im suprised at Softus....the physics of it are really quite simple.

 

[Softus]

the physics of it are really quite simple.

Quite so. And if you read my posts again you might realise that I wasn't overtly challenging anyone's solution, just highlighting the fact that the "peters out in 30 seconds" symptom would be misleading to anyone for whom the physics are not simple.

The OP has since clarified his description, and I thought all was well until you posted your little dig.

 

[HarrogateGas]

the physics of it are really quite simple.

Quite so. And if you read my posts again you might realise that I wasn't overtly challenging anyone's solution, just highlighting the fact that the "peters out in 30 seconds" symptom would be misleading to anyone for whom the physics are not simple.

The OP has since clarified his description, and I thought all was well until you posted your little dig.

it was not a dig, i was actually praising your knowledge as you rarely get it wrong on this forum but in this instance you did, take it gracefully........we all make mistakes! It was not dig but if you want to be an ar*s about it then fine, take it as a dig.

 

[pannierstan]

Having worked in the industry for many, many years perhaps its just that I have got used to customers explanations of what the problem is.

The main thing is that on this occasion I am glad I managed to point a member of this forum in the right direction and that he obviously has enough knowledge to solve the problem from there.

Stan

 

[Softus]

it was not a dig, i was actually praising your knowledge as you rarely get it wrong on this forum

I apologise - I misinterpreted your comment, and thank you for the real meaning.

...but in this instance you did, take it gracefully........we all make mistakes!

I wouldn't expect you to have read all of my posts, but on every single one of those rare times that I've been wrong I've stated it quite clearly, and also apologised where it was appropriate.

However, on this topic I genuinely don't see where I've been wrong. pannierstan was utterly correct, but the point I've been making was soundly missed by everyone except Rich_W, viz:

The fact that cold water pressure is OK...

So, if you think I'm wrong then you must, in order to be consistent, also believe that he was wrong.