System Working But No Hot Water At Taps

[iridium]

Hi Everyone,

Was hoping I could pick your brains before calling in a plumber. I've done a forum search but can't find anything that matches.

I have a gas boiler that feeds a hot water cylinder. All of a sudden hot water has stopped coming out of all our hot water taps and shower.

The strange thing is, the rest of the system seems to be working fine (although I'm guessing it's not otherwise this wouldn't be happening). If I turn the programmer on, the boiler lights up and heats the water in the storage tank to 60c (as set on the cylinder thermostat) and the stops (as it should). The central heating also comes on as it should, and yet I'm getting cold water out of the hot water taps.

I'm really racking my brains here wondering what could be causing this. Any ideas?


Thanks in advance.

Cheers,
M

 

[Resolute]

Have you had any work done recently?

 

[iridium]

Thanks for the quick reply Resoloute.

No work at all done recently. Just stopped working all of a sudden.

Just asked the Mrs and she said it happened after turning off the mains water supply for something. Could that have effected the hot water system? Water is still coming out of the hot water taps. It starts cold, gets luke warm for a couple of seconds and the switches back to being cold. I'm guessing that could just be caused by cross-heating of pipes through the walls?

 

[SimonG]

Do you have water coming out the overflow? Any mixer taps or showers? If so do they have check valves on the supplies?

 

[iridium]

No water coming out of the overflow.

We do have some mixer taps and a mixer shower. Not sure about the check valves. We've still got the same mixer shower that was installed in the house 20 years ago when it was new. The mixer taps are a few years old.

Hope that helps?

 

[Keefy]

So you've got hot water at 60 degrees in the cylinder and it's not reaching your taps?

 

[SimonG]

Close your cold water stop tap again and open the hot tap. Do you get hot water?

 

[iridium]

Correct.

Checked an exposed part of copper on the cylinder with a I.R thermometer. Went from cold to 60c at which point the boiler cut out. Only cold water from all the taps and shower though.

 

[jtsplumbing]

Have you checked the large tank in the loft ? maybe ball valve as stuck and tank is empty

 

[iridium]

Hi,

There's no header tank in the loft.

We've got one of those combination cylinders with two compartments. Have just had a look inside the top compartment and not only is the water dirty, but when I push down the ball cylinder, no water enters.

The top tank is about 8/10ths full though. Hope that makes sense.

We do have water coming out of the hot water taps though. It's just cold. If the cylinder was empty, wouldn't that mean the taps would run dry?

 

[jtsplumbing]

Ok top part has water in it ! but no water coming out of ball valve when depressed, so must have dirt blocking ball valve, and if water in top tank is dirty you may have had dirty water through mains ! any work going on in area (Water) is water in top tank hot ? you could have a blockage in the feed pipe from top tank into hot part.

 

[iridium]

Close your cold water stop tap again and open the hot tap. Do you get hot water?

Have just turned off the mains water as suggested and now no water is coming out of the cold OR hot taps!

That must narrow it down to something...

 

[iridium]

Ok top part has water in it ! but no water coming out of ball valve when depressed, so must have dirt blocking ball valve, and if water in top tank is dirty you may have had dirty water through mains ! any work going on in area (Water) is water in top tank hot ? you could have a blockage in the feed pipe from top tank into hot part.

No mains water work going on in the area as far as I'm aware.

The water in the top part did get hot as well this morning. Also read my above post...

 

[jtsplumbing]

Have just turned off the mains water as suggested and now no water is coming out of the cold OR hot taps!

That must narrow it down to something...

Ok so turn water back on, you seem to have a blockage on your hot water tank, it's just strange that you can only get cold water from hot tap, I take it that the tank is hot ? if so what happens if you let a hot tap run ? does it slow down and stop ? or start to warm up ?

 

[iridium]

Ok so turn water back on, you seem to have a blockage on your hot water tank, it's just strange that you can only get cold water from hot tap, I take it that the tank is hot ? if so what happens if you let a hot tap run ? does it slow down and stop ? or start to warm up ?

Strange I know. I can't get my head around it.

The tanks definatly gets hot, both to the touch and when measured with a thermometer. If I let the hot water taps run it carries on with cold water. Doesn't slow down at all. Have left it open for nearly 10 minutes and it's still cold.

Why would no water come out of the hot water taps when the mains is off though, but cold water comes out hot taps when the mains is back on? Does that means that the mains water is getting in to the hot water piping somehow?

 

[mutley racers]

Testing

 

[iridium]

/////

 

[nickelarsed]

Sounds like you have mains pressure coming through a mixer tap. That's why no hot can get to the taps. I wonder if you turn the mains down, but still open will the hot water be able to flow out of the cylinder. Maybe you have had a block feed for some time but not noticed since the tank was getting back fed from the mains. Now you have re opened the main stop tap fully the extra flow is stopping the hot distribution. Never seen this but only reason I can think of. Either way you will need to clear that feed, and probably need a new mixer. Maybe time to call a plumber in

 

[iridium]

Sounds like you have mains pressure coming through a mixer tap. That's why no hot can get to the taps. I wonder if you turn the mains down, but still open will the hot water be able to flow out of the cylinder. Maybe you have had a block feed for some time but not noticed since the tank was getting back fed from the mains. Now you have re opened the main stop tap fully the extra flow is stopping the hot distribution. Never seen this but only reason I can think of.

Interesting idea. Will check and report pack.

 

[nickelarsed]

Sounds like it's blocked/airlocked now otherwise hot would run with the mains off. But may be worth isolating any mixer taps, see if that stops the flow from the hot.

 

[Dotty]

Debris in the ballvalve seat.

 

[iridium]

Interesting idea. Will check and report pack.

Have tried what you said. Same problem as before.

 

[stevetheplumber]

my guess would be the shower is crossing water into the hot water pipework this should cause the tank at the top of the cylinder to overflow however if there is a stopcock on the hot water pipework this would act as a non return valve and stop the mains water getting back to the tank

 

[iridium]

Thanks for all the suggestions 🙂

Will have a good look again tomorrow and if I cant figure it out, will get a plumber in.

 

[stevetheplumber]

shower or another mixer i should have said