Dripping Overflow from unvented system (w/pics)

[barki]

Hi

Just moved into a new house - I'd got to know my old vented system pretty well and did quite a bit of successful DIY work on it.

However - This new place has an unvented / pressurized system, and one of the overflows is dripping.

For the H/W, in the attic there is a cylinder with a smaller expansion bottle next to it. See photo below. Note: there is a vented tank for the C/H expansion.

The boiler is an oil-burning 'wallstar' with no obvious faults.

My problem isn't a critical one (I hope) - but I've noticed that every evening/morning when the boiler is running DHW, one of the overflow pipes drips.

The pipes in this house are all buried in the wall so I can't see where this overflow runs to/from which is annoying. There are two, both located only about 6' from the boiler location and about 6" from the outside ground level, rather than poking out of the eves like I'm used to.


I can't figure out why it's dripping, here are a few other bits of info to help;

- It drips constantly while DHW is running. About 1 drip per second.

- It does it in all weathers (hot or cold)

- I can't see any leaks or issues in the plumbing system elsewhere.

- Boiler seems to function normally, no noises, no smoke,

- I doubt it's related, but there is a water softener installed in the location of the original HW cylinder (before unvented system installed).

- The unvented system was installed 2011.


Really grateful if anyone can help

Cheers,

Tom

 

[barki]

 

[bernardgreen]

The dripping pipe is probably NOT an over flow but a badly installed condensate drain from the boiler. Condensing boilers produce a liquid ( water with dilute acids ) when they condense the water vapour produced by burning the fuel

It should be arranged that the condensate liquid is taken to a drain or a properly constructed soak away

 

[picasso]

More likely the expansion vessel is flat, there is a tundish in front of the cylinder can you see if there is a drip going through it ?

 

[dilalio]

Condensate drainage would (or should) be white overflow plastic pipe, not copper.
As Picasso says, it is likely a pressure release valve letting by from the vessel and releasing water to the discharge pipework.
Put some tissue in the tundish for a few minutes while running the DHW and see if it gets soaked.
Use a footpump to check the air pressure side of the expansion vessel.

 

[bernardgreen]

The reason I suspect it is the condensate drain is the bright blue deposits on the end of the pipe which appear to be the same colour as copper sulphate.

Copper sulphate would be produced by the action of sulphuric acid in the condensate on the copper of the pipe. "clean water" would produce copper oxide which is green rather than blue

 

[picasso]

If it was condensate the copper pipe would be disintegrating after five years of use.

 

[dilalio]

Exactly! And it wouldn't meet regs when system was installed... Larger 22mm copper bore for d2 discharge.

 

[OvertonPlumber]

The reason I suspect it is the condensate drain is the bright blue deposits on the end of the pipe which appear to be the same colour as copper sulphate.

Copper sulphate would be produced by the action of sulphuric acid in the condensate on the copper of the pipe. "clean water" would produce copper oxide which is green rather than blue

More likely just baco flux being washed out the pipework

 

[polesapart]

Use a footpump to check the air pressure side of the expansion vessel.

Having first turned off the water to the cylinder and left a hot tap open.

 

[dilalio]

In fact OP, Google the procedure for checking pressure vessels and PRVs or call in an engineer.

 

[bernardgreen]

Exactly! And it wouldn't meet regs when system was installed... Larger 22mm copper bore for d2 discharge.

If it was condensate the copper pipe would be disintegrating after five years of use.

Since when has every installation been fully compliant with the regulations.? One of our neighbours has an external condensate drain in copper, bodged install about 8 years ago. Pipe looked intact this morning. It might be that the inside of the pipe is coated with copper salts that are protecting the copper from further attack. Flow of condensate is too low and slow to wash away that accidentally formed protective lining.

Put some tissue in the tundish for a few minutes while running the DHW and see if it gets soaked.

Or pour some dye coloured water into the tundish while some one looks to see if it comes out of the suspect pipe.

 

[dilalio]

Any feedback OP???

 

[Agile]

Usually copper pipe exposed to the atmosphere eventually oxidises slightly and then absorbs carbon dioxide from the atmosphere and produces copper carbonate which has a whitish green colour.

You can see that on many domes on buildings!

 

[Agile]

The large copper pipe is likely to be the pressure release valve vent from the Main unvented cylinder.

But all work on that type of cylinder should only be done by a qualified person with the appropriate G3 qualification.

So not a DIY job.

Its clearly not a "new house" as you state. So when moving into a used house its most sensible to get the boiler serviced and the system checked over.

Tony