icicle forming in overflow pipe

[pooksahib]

Hopefully someone will be able to solve this little problem for me as I can't imagine what's causing it. Yesterday, I dislodged a chunky, foot long icicle from the overflow pipe of the cold water tank. Ice had also formed to about 6 inches inside the pipe. I cleared all the ice out and, for the rest of the day, there was a slow, continuous drip of water from the pipe onto the pavement below. This morning, following another cold night, the icicle had reformed as big as yesterday, almost blocking off the pipe entirely. After removing the ice, I went up to the loft to check the tank (there's only the one since the heating is all electric) and it was fine – water level just below the overflow.

There was an icicle in the same place a few weeks ago but I gave it no thought as it was just a one night cold snap. I'm pretty sure that, in the intervening period, there's been no dripping from the overflow pipe as I'd have surely noticed it. If the tank isn't overflowing, can anyone suggest a reason for the icicle formation (including the ice inside the pipe) during this cold weather? The water forming the icicle must originate somewhere...

Supplementary question 1: there's a pipe attached to the lid of my tank. What is this for and where does the pipe go (I couldn't follow it as I lost the trail under the loft insulation...)?

Supplementary question 2: While I had the lid of the tank off, I had Mrs pooksahib flush the WC and run the bath's cold tap. This was so I could (hopefully) watch the tank emptying and refilling properly. But there was no activity at all despite the bath tap running for at least a minute. I was expecting the main inlet to open immediately. Does this indicate a problem or does it maybe take quite a bit of water usage before the tank refills?

Many thanks to anyone who assists me.

 

[mogget]

Hopefully someone will be able to solve this little problem for me as I can't imagine what's causing it. Yesterday, I dislodged a chunky, foot long icicle from the overflow pipe of the cold water tank.

I had the same thing happen a few weeks ago, and it mystifies me, too. I was out for the day and when I got home I noticed an icicle on the warning pipe. My first thought was along the lines of 'oh, ship' and, worried, I went to check the cistern in the attic. There was nothing wrong with it, the water was about 100mm below the overflow as normal.

I noticed several other houses with the same thing happening. I think it may be due to the water in the cistern being warmer than the outside air, that the vapour from the cistern is exiting through the overflow and condensing on the way out. I can't be sure though.

Question 1 - if it's a 22mm copper tube bent in an arch and ending above the water level in the cistern, that's the vent pipe for the hot water cylinder.

Question 2 - It sounds like your bath and toilet are supplied with mains water. Running a hot tap will use water from the cold water cistern.

 

[JohnD]

perhaps it feeds the hot water.

if the ball valve is dripping slightly, then it will not reach the overflow as long as you run taps from time to time. Overnight, or at other times when taps are not being run, the drip will slowly increase the level.

Easiest and cheapest fix is to replace the valve with a new one (you can repair the old one if you want, but it is more comfortable to do this at your leisure on the kitchen table, and keep it for a spare, rather than hunched in a dark cold loft)

While you are up there, look for a Feed & Expansion "header" tank for your boiler. if there is one, look at the water level, and decide if the F&E is higher or lower (relative to ground level) than the cold water cistern. this may be relevant.

Also satisfy yourself that all pipes and tanks are well-insulated.

If (as we think) the cold taps are mains-fed and the hot taps are tank-fed, identify all the mixer taps you have (including showers) as these can have an internal leak, especially if they are thee Ceramic type with a joystick. Look to see if they have service valves to isolate them. Feel the hot pipe top each tap and see if it is surprisingly cold ten minutes after use. This will be your next thing to investigate if the new ball-valve does not fix it.

 

[pooksahib]

Many thanks, mogget and JohnD. mogget, although you say you 'can't be sure', your explanation of the icicle sounds extremely plausible and I appreciate your help. I'll wait for warmer weather and, if there's no drip, give you the credit. As regards the vent pipe for the hot water cylinder, what's going on there exactly?

You mention a header tank, JohnD and I certainly had one in my last house (which had gas central heating). This house has electric heaters and I see no sign of a second tank in the loft. There's no boiler either, come to that! The water is heated by off-peak electricity.

Thanks again, lads.

 

[mogget]

As regards the vent pipe for the hot water cylinder, what's going on there exactly?

Thanks again, lads.

Ladette actually, but thanks anyway

The vent pipe on the hot water cylinder is a safety device in case a thermostat sticks on, causing the water to boil. It allows the steam to escape, preventing a possible explosion.

Some time ago this situation occurred in a local authority house. The cold water cistern was not supported properly and split due to the heat. Tragically, the hot water came through the ceiling and scalded a young child who later died.

It's the law now that all new immersion heaters must have a second overheat thermostat, which must be reset manually.

 

[pooksahib]

Hi mogget and thanks for that additional info. As a matter of interest, I took a look round the neighbour's house this morning and they're sporting a lovely icicle hanging off their overflow which made me happy.

Please accept a virtual 'mwah, mwah' for your assistance.