Water from boiler overflow pipe

WIAWSNB

If the pipe is copper, as you suggested in your OP, then it's the safety discharge pipe. Ie, it kicks in to release excess system pressure, usually tripping at around 3bar, It is almost certainly that pipe.
You say the pressure rises to around 2bar when the system is hot. It's worth keeping an eye on this as it initially heats up from cold - Ie, monitor it over, say, the first 20 minutes.
I'm guessing that you need to top up the pressure regularly? Ie, when the system cools down, the pressure then plummets? If the boiler is discharging water regularly from it's sealed system, then the overall pressure must be falling, and therefore needs refilling - can you confirm, please?
As said by others, this is not necessarily a big issue. It could just be that your EV needs repressurising, and very likely the safety valve itself will need replacing as they usually leak once 'blown' open.
Not a DIY task, so you need your service fellow to confirm all this.
If the EV needs replacing, you are probably talking of around £50 for this part, and £20 for the valve. A good hour's work, perhaps more. 
If the EV just needs repressurising, then it's 10 minutes labour only.

Albermarle

JohnB47 said:

grumpy_codger said:

It's 'pressure relief', not 'overflow'. If water leaks from this pipe this has to result in pressure dropping in the sealed CH system. This is usually caused by faulty expansion vessel of the boiler (or faulty pressure relief valve).

Not necessarily faulty. It could be that it simply needs repressurised and therefore it is not able to take up the pressure generated by the CH water being heated.

As already asked, what is the system pressure reading hot/cold?

Could it be that the dripping pipe is actually the waste condenser water pipe? It's perfectly normal for that to drip at any point  - hot water being run or CH running. The condenser pipe on my system is white plastic and is internal, connected to the waste under the kitchen sink.

Condensate pipe that goes outside, would normally be connected to the waste water system somewhere outside.
Although the liquid is not toxic as such, it is mildly acidic, so not ideal for it be just dripping on the ground. 
Condensate pipe is also plastic, whilst the offending pipe in this case is copper. 

JohnB47

Albermarle said:

JohnB47 said:

grumpy_codger said:

It's 'pressure relief', not 'overflow'. If water leaks from this pipe this has to result in pressure dropping in the sealed CH system. This is usually caused by faulty expansion vessel of the boiler (or faulty pressure relief valve).

Not necessarily faulty. It could be that it simply needs repressurised and therefore it is not able to take up the pressure generated by the CH water being heated.

As already asked, what is the system pressure reading hot/cold?

Could it be that the dripping pipe is actually the waste condenser water pipe? It's perfectly normal for that to drip at any point  - hot water being run or CH running. The condenser pipe on my system is white plastic and is internal, connected to the waste under the kitchen sink.

Condensate pipe that goes outside, would normally be connected to the waste water system somewhere outside.
Although the liquid is not toxic as such, it is mildly acidic, so not ideal for it be just dripping on the ground. 
Condensate pipe is also plastic, whilst the offending pipe in this case is copper. 

Yes indeed. But corners are cut and mistakes are made.

Like my bathroom fitter neglecting to fit a support for the pipe that feeds water from the boxed in loo cistern to the loo. Discovered after a large stain appears on the ceiling of the room below.

johnnyren

Albermarle said:

JohnB47 said:

grumpy_codger said:

It's 'pressure relief', not 'overflow'. If water leaks from this pipe this has to result in pressure dropping in the sealed CH system. This is usually caused by faulty expansion vessel of the boiler (or faulty pressure relief valve).

Not necessarily faulty. It could be that it simply needs repressurised and therefore it is not able to take up the pressure generated by the CH water being heated.

As already asked, what is the system pressure reading hot/cold?

Could it be that the dripping pipe is actually the waste condenser water pipe? It's perfectly normal for that to drip at any point  - hot water being run or CH running. The condenser pipe on my system is white plastic and is internal, connected to the waste under the kitchen sink.

Condensate pipe that goes outside, would normally be connected to the waste water system somewhere outside.
Although the liquid is not toxic as such, it is mildly acidic, so not ideal for it be just dripping on the ground. 
Condensate pipe is also plastic, whilst the offending pipe in this case is copper. 

As you face the boiler the pipe is coming down from the farthest left connection , comes down six inches then out the back wall to outside ,    The pressures all seem fine as far as the boiler goes storing between 1.5 and 2 

WIAWSNB

johnnyren said:

Albermarle said:

JohnB47 said:

grumpy_codger said:

It's 'pressure relief', not 'overflow'. If water leaks from this pipe this has to result in pressure dropping in the sealed CH system. This is usually caused by faulty expansion vessel of the boiler (or faulty pressure relief valve).

Not necessarily faulty. It could be that it simply needs repressurised and therefore it is not able to take up the pressure generated by the CH water being heated.

As already asked, what is the system pressure reading hot/cold?

Could it be that the dripping pipe is actually the waste condenser water pipe? It's perfectly normal for that to drip at any point  - hot water being run or CH running. The condenser pipe on my system is white plastic and is internal, connected to the waste under the kitchen sink.

Condensate pipe that goes outside, would normally be connected to the waste water system somewhere outside.
Although the liquid is not toxic as such, it is mildly acidic, so not ideal for it be just dripping on the ground. 
Condensate pipe is also plastic, whilst the offending pipe in this case is copper. 

As you face the boiler the pipe is coming down from the farthest left connection , comes down six inches then out the back wall to outside ,    The pressures all seem fine as far as the boiler goes storing between 1.5 and 2 

So you don't have to top up the pressure regularly? 

johnnyren

WIAWSNB said:

johnnyren said:

Albermarle said:

JohnB47 said:

grumpy_codger said:

It's 'pressure relief', not 'overflow'. If water leaks from this pipe this has to result in pressure dropping in the sealed CH system. This is usually caused by faulty expansion vessel of the boiler (or faulty pressure relief valve).

Not necessarily faulty. It could be that it simply needs repressurised and therefore it is not able to take up the pressure generated by the CH water being heated.

As already asked, what is the system pressure reading hot/cold?

Could it be that the dripping pipe is actually the waste condenser water pipe? It's perfectly normal for that to drip at any point  - hot water being run or CH running. The condenser pipe on my system is white plastic and is internal, connected to the waste under the kitchen sink.

Condensate pipe that goes outside, would normally be connected to the waste water system somewhere outside.
Although the liquid is not toxic as such, it is mildly acidic, so not ideal for it be just dripping on the ground. 
Condensate pipe is also plastic, whilst the offending pipe in this case is copper. 

As you face the boiler the pipe is coming down from the farthest left connection , comes down six inches then out the back wall to outside ,    The pressures all seem fine as far as the boiler goes storing between 1.5 and 2 

So you don't have to top up the pressure regularly? 

No it doesn’t appear so ,  the gauge seems to stand firm at just under 2 bar 

WIAWSNB

johnnyren said:

WIAWSNB said:

johnnyren said:

Albermarle said:

JohnB47 said:

grumpy_codger said:

It's 'pressure relief', not 'overflow'. If water leaks from this pipe this has to result in pressure dropping in the sealed CH system. This is usually caused by faulty expansion vessel of the boiler (or faulty pressure relief valve).

Not necessarily faulty. It could be that it simply needs repressurised and therefore it is not able to take up the pressure generated by the CH water being heated.

As already asked, what is the system pressure reading hot/cold?

Could it be that the dripping pipe is actually the waste condenser water pipe? It's perfectly normal for that to drip at any point  - hot water being run or CH running. The condenser pipe on my system is white plastic and is internal, connected to the waste under the kitchen sink.

Condensate pipe that goes outside, would normally be connected to the waste water system somewhere outside.
Although the liquid is not toxic as such, it is mildly acidic, so not ideal for it be just dripping on the ground. 
Condensate pipe is also plastic, whilst the offending pipe in this case is copper. 

As you face the boiler the pipe is coming down from the farthest left connection , comes down six inches then out the back wall to outside ,    The pressures all seem fine as far as the boiler goes storing between 1.5 and 2 

So you don't have to top up the pressure regularly? 

No it doesn’t appear so ,  the gauge seems to stand firm at just under 2 bar 

Ok, summat is amiss :-)
IF that pipe is the safety discharge pipe, and IF you don't need to top-up the pressure to compensate for this loss, and IF it is a combi boiler, then, um, er, it's um...
Possibly your P2P exchanger is perforated, so it's allowing mains water into the system. 
Or a similar component which has both mains and system water within - a hydrobloc (stupid name) or similar.
Can't think of anything else. 

Vortigern

johnnyren said:

WIAWSNB said:

johnnyren said:

Albermarle said:

JohnB47 said:

grumpy_codger said:

It's 'pressure relief', not 'overflow'. If water leaks from this pipe this has to result in pressure dropping in the sealed CH system. This is usually caused by faulty expansion vessel of the boiler (or faulty pressure relief valve).

Not necessarily faulty. It could be that it simply needs repressurised and therefore it is not able to take up the pressure generated by the CH water being heated.

As already asked, what is the system pressure reading hot/cold?

Could it be that the dripping pipe is actually the waste condenser water pipe? It's perfectly normal for that to drip at any point  - hot water being run or CH running. The condenser pipe on my system is white plastic and is internal, connected to the waste under the kitchen sink.

Condensate pipe that goes outside, would normally be connected to the waste water system somewhere outside.
Although the liquid is not toxic as such, it is mildly acidic, so not ideal for it be just dripping on the ground. 
Condensate pipe is also plastic, whilst the offending pipe in this case is copper. 

As you face the boiler the pipe is coming down from the farthest left connection , comes down six inches then out the back wall to outside ,    The pressures all seem fine as far as the boiler goes storing between 1.5 and 2 

So you don't have to top up the pressure regularly? 

No it doesn’t appear so ,  the gauge seems to stand firm at just under 2 bar 

Gauges sometimes stick if the capillary is blocked. My gauge didn't rise when I was repressurising the system, resulting in the PRV opening.
johnnyren does the pressure go above 2 when you top up the water?

Is the filling loop permanently connected with the valves open? It shouldn't be, but if it is, it will keep the system at mains pressure and replace any lost water.