Hot Water Tank Tundish Filling?

[Yardelli]

Hi all - went to switch on my central heating this morning and could hear a drip from my Hot Water Tank area. What appears to be the pipe running down from the Pressure Release Valve has an inline Tundish. This seem to be filling UP with water? Dripping down I would have expected it to be the valve but its definately filling up with the system on? The pipe then goes off out the back wall - presumably to the outside overflow pipe. Could it be that this is frozen in the current weather? What would make it keep filling though? Any ideas gratefully appreciated....

 

[ianmcd]

what make and model of hot water tank do you have ? is it an unvented cylinder ? if it is you probably need to re-establish the expansion bubble will tell you how to on the side of the cylinder very easy to do.

 

[Yardelli]

Hi Yes - its an Unvented Heater System - Excelsior Model 175? Not sure if it tells me anywhere about the air bubble. Any idea where / how I can find out how to do? Surely if there was a need to add an air bubble this would be indicated but overflow being seen dripping down into the Tundish? This is not happening - the Tundish is filling from below?

 

[ianmcd]

If the Tundish is filling from below you have a back up somewhere, I have never seen this happen, you need to look and see if other appliances are sharing the discharge pipe and are releasing and backing up, please come back on and let us know how you get on I cant imagine how a tundish could fill from the bottom as no appliances should share outlet pipework

 

[Yardelli]

Cheers anyway Ian. I'm wondering if the Boiler is connected to the outlet and forcing water upwards? I did have to re-pressurise the Boiler the other week though its sat at the correct pressure according to the manual on the gauge. The only thing I can think of is the overflow outlet is frozen over? It was -5 here the other night.....

 

[ianmcd]

yes it does sound like it has frozen over as you say but two outlets for presssure releif valves or D2s to give them their correct name should not be joined sounds as though yours are

 

[Yardelli]

Thanks Ian - I'll let you know what I find!

 

[Yardelli]

OK update - Ian - I am a bit of a novice at this.... After much web browsing it seems what I was looking at was not as described. Returned home to work last night. The Tundish is continuing to fill however I can now see that the pipework that carries on from below the Tundish and carries on outside the wall is also linked into by another pipe that does contain a Caleffi Pressure Relief and Reducing Valve. The Relief valve has a twistable 6 bar Red coloured head on. This is dripping from the thread. Seems this may be the cause after all - I'm guessing the valve is bypassing water thats feeding into the overflow outlet pipe. I turned the upstairs water off with the isolation tap in the Heater Tank room where this all is overnight. The Water on the Tundish cleared so my overflow must be clear. Any advice for a nervous novice on changing that PRV appreciated.
Its the same as this one:
http://www.ec21.com/offer_detail/Sell_caleffi_CE_safety_valve--10201516.html

 

[ianmcd]

Think you are still mistaken mate that is a 3 bar system PRV and not a 6 Bar domestic water PRV the one you have highlighted is typical to boilers and not HW cylinders, 6 Bar ones are usually Blue but not always , confusing I know

 

[Yardelli]

It says 6 bar on the top of it Ian?
This may be a better shot of it:

Its dripping from the thread where that arrow is. It was fine this morning until I turned the Hot Water on and the Water Heater Tank was obviously demanding water.....I then also get the feed that also routes into the overflow with the Tundish causing it to overflow.

 

[Yardelli]

OK sorted - The Heater Tank overflow was frozen solid. Got on my extension roof where it vents out and a pile of pipe shaped icicles had dropped out.
Not a drop from the system now - I'm still curious as to why the Relief valve was dripping. The Mains inlet vents through the valve and joins into the overflow excess water. I can only presume as its a one-way valve it did not like forced water pressure being sent the other (wrong) way. Fine now.......