Identifying source of dripping water on unvented system

[Frustrated Puma User]

Good morning eveyone.

I'd like to ask for your thoughts and opinions please on identifying the source of water dripping from an external copper pipe please.

In my townhouse I have an unvented system with a gas boiler which is made up of the following.

Ideal ICOS HE15 condensing boiler.
Kingspan Range Tribune HE unvented cylinder.
Contra-Flex expansion vessel for the heating. Flamco Airfix P Potable Water expansion vessel.
Myson Power Extra valve
Circulating pump

The system was serviced a week ago - the boiler all checked out OK and was cleaned of deposits, and the potable water expansion vessel was removed, recharged and refitted. The cylinder was drained and refilled also. The heating expansion vessel I'm told is OK also.

There is water dripping from the 22mm copper pipe that comes out of the wall at ground level at the rear of the property. This drips at a rate of approx. 1 drip per second for 3 seconds, followed by 4 drips in quick succession inside the next 2 seconds. Then the cycle repeats. The water drips from this pipe constantly regardless of whether the HW is on, the CH is on, or both are on. The temperature of the dripping water is always cold, and the rate of flow never changes either under any condition. The tundish never passes any water and is always bone dry.

Here are some photos of the setup.

I'm selling the house and would like to get this fixed so the new owner has no issues. I will be using the same engineer to fix it but am just curious as to what could be causing the issue. The engineer said it could be that the potable expansion vessel might need replacing but I'm not certain.

Any thoughts and advice will be greatly appreciated.

Thanks in advance,

Gary

 

[Frustrated Puma User]

I forgot to add, that the dripping has been happening since I bought the housein 2021, and has not changed following each annual servicing. The system was installed in 2020. Thank you.

 

[Madrab]

By the sounds of it, it is either the expansion Pressure Relief Valve (PRV) that is passing or whatever else is connected to it, more than likely the the Central Heating(CH) PRV.

There also looks to be a tundish missing unless it's out of view somewhere. There is one on the Temp PRV on the unvented but doesn't seem to be one on the Unvented (UV) Combination Valve PRV/CH PRV D1>D2

Usually these 2 15mm Discharge (D) pipes would be connected, then run into a tundish with a 22mm D2 outflow, that would allow a visual indication if there's an expansion issue from either the CH or UV. As the drips are cold then chances are it will be from one of these.

Was this pointed out at service time? If so then the biggest issue is that not one of your service engineers has caught this and sorted it out. It is a service item. It may be as simple as an Expansion Vessel (EV) needs re-charged or a PRV that's not re-sealed properly and needs replaced

 

[Frustrated Puma User]

Thank you Madrab, what you say makes total sense. I did think that there should be a second tundish as I have seen 2 on photos of other people's setups online. You're also right that it hasn't been called out durimg servicing. I'll make sure the engineer sorts the issue. Thank you once again.