Gear Head

iTrader: (2)

Forgive me for being a heating numpty but does anyone know what would cause water to constantly trickle through this section?

john banks

To my understanding, this is called a tundish and its purpose is for the building user to see and hear that something is venting often through a pressure release valve (the red thing from the looks of it) due to excessive pressure, or a leaking pressure release valve. It is a safety device, and requires competent investigation.

Gear Head

iTrader: (2)

Thanks John!

alcazar

iTrader: (2)

As above, the pressure release valves have a way of NOT lasting as long as you think they should.

The occasional drip, or small flow is caused by the valve venting pressure from the vessel. If it drips all the time, the seat or washer is probably shot.

Over here in France they aren't repairable, only replaceable.

Cost about €35 too.....

DJ Dunk

iTrader: (5)

As above. Had the same on my unvented system too. The TPR (Temperature Pressure Relief) valve needed replacing (£35 part).

Only thing was on mine, the idiots haven't installed a tundish, so the first warning was boiling water pouring from the front of the house . . . over the front door.

mamoon2

Stupid place to put an overflow that!!

Gear Head

iTrader: (2)

Home builder contacted and an engineer is coming on Monday. (house it still under warrenty so i don't pay a penny!)

Dr.No

Just to add to this - I spent AGES and quite a lot of money changing components on my unvented system when I had a problem with water dribbling from the pressure relief valve.

In the end it transpired to be a cheap/crap mixer tap in one of the ensuites that was allowing cross flow from cold to hot. (ie cold water at about 3 bar or so to creep into the hot pipe - and hence overpressurise the hot cylinder). This was eventually fixed by putting a decent non-return valve in the hot water outlet of the cylinder. Make sure you have a non-return valve in the hot output from the cylinder.

FYI I diagnosed this - eventually - by running a hot tap until the hot output pipe of the cylinder was hot to the touch, and then shutting the hot tap off and continuing to touch the hot pipe from the cylinder. It was getting noticeably colder quite quickly on the section of pipe furthest away from the cylinder, but I could feel the cold moving down and towards the cylinder. Not difficult to then deduce that it's cold water backflowing.

HTH

DN

Mog

It may not be the cylinder as that relief pipework has a tee in it and so also may serve the central heating as well.

Mog

It sounds as though your unvented system isnt installed correctly as the cold water take off should come from the balanced feed connection on the combination valve to prevent this sort of thing happening.

JGlanzaV

iTrader: (3)

It will require another tundish fitted above the t so you can identify in future what has lifted,

Should never T saftey valves in together really, but if they do insist on doing it mke them fit nother tundish above the t so you can see what is going on in future

It does not comply as is

Dr.No

Well, there's a pressure-reducing valve on the incoming mains - dropping everything down to around 4 bar. So - normally, and if I wanted the hot water at 4 bar - they'd be both running of a single balanced feed. However, there's a variable pressure-reducing valve (with gauge) on the cold feed to the hot tank - which is set down to around 3 bar.

Having the hot running at lower pressure (and the way it's possible to get soaked with cold water when turning on a cold tap, it wouldnt be pleasant if the hot was equally as vicious!) means that the cold can backflow into the hot from crap taps. It was only happening with one tap in one ensuite, but it was enough to cause a headache (and many other replaced system components!).

DN

500

Which as Mog said, is wrong, and if they were on a balanced supply, you possibly wouldn't have had a problem.


You also shouldn't touch an unvented cyl yourself without being suitably qualified, they are a bomb with safety devices.