Overflow pipe from heating system

[noobiediyer]

My heating system has an overflow pipe that comes out of the side of my house. For a while I've noticed water stains along the brick that made me feel it was overflowing at some point but I've never seen it happen directly.

There's 3 things that are connected to the overflow pipe, there's a pipe coming out of the system boiler (Vaillant ecoTec plus 637), an overflow/overpressure pipe coming out of the Megaflo tank and some pipe coming out of the bottom of an expansion vessel (this is mounted on the wall near the Megaflo). The megaflo pipe has a break in the pipe near the megaflo that looks like this:

So if this is where the leak is then it would be obvious, however it is always very dry and doesn't look like it is putting out water at all.

Anyway, I pointed a continously recording camera at the pipe on the outside of the house and noticed that it slowly drips/leaks water for 5 or 10 minutes when I have scheduled the water to heat.

I have the water scheduled to heat in the early morning for 1 hour every day. I noticed the leaking was happening about 30 minutes after the start of the water heating. As a test, I changed the schedule to heat the water 2 hours earlier and the leaking changed accordingly so it still happened 30 minutes after the start of the water heating.

So it seems like it's related to the water heating. So my question is, is this normal? Is it likely to be coming from the boiler or the expansion vessel? Should I be concerned or what else should I have checked?

 

[CountryFan]

Sounds like they have combined the condensate pipe and D2 safety discharge and possibly the safety discharge from the boiler. Does the boiler have a pressure gauge and is there a gauge near the unvented cylinder? If the pressure doesn't rise in these when demand is on, then it could just be the condensate pipe.

Are you able to check if the condensate pipe is connected to this affected pipe?

 

[endecotp]

There's 3 things that are connected to the overflow pipe, there's a pipe coming out of the system boiler (Vaillant ecoTec plus 637), an overflow/overpressure pipe coming out of the Megaflo tank and some pipe coming out of the bottom of an expansion vessel (this is mounted on the wall near the Megaflo).

We need to know exactly what the pipe from the boiler is, i.e. is it the condensate or pressure relief. Maybe post a photo of the bottom of the boiler showing the pipe connections.

 

[Madrab]

So it seems like it's related to the water heating. So my question is, is this normal

No, it shouldn't be doing it.

scheduled the water to heat.

I'd hazard a guess that if it's doing it when the HW is calling then it's the expansion PRV that's passing when the cylinder is up to temp. Given its a megaflop then chances are the bubble needs to be recharged. It's the one thing on an unvented that the user can do, there should be instructions on the cylinder as to how to do that.

Alternatively get the system serviced and get them to check each (T)PRV.

 

[noobiediyer]

I'm pretty sure it's not the condensate pipe. Picture of underneath the boiler:

The copper pipe highlighted in red is the one that connects to the outside pipe. The white plastic pipe behind it (highlighted in green) I believe is the condensate one which is connected to a plastic waste pipe outlet (same one connected to the waste washing machine pipe).

 

[noobiediyer]

The other pipe from the expansion vessel is this one highlighted in green:

 

[CountryFan]

So you have an expansion related issue somewhere and will need an engineer to attend

 

[noobiediyer]

So you have an expansion related issue somewhere and will need an engineer to attend

Just for my understanding, how can I be sure it's not the boiler and that it's definitely the expansion vessel causing the issue?

 

[CountryFan]

Just for my understanding, how can I be sure it's not the boiler and that it's definitely the expansion vessel causing the issue?

I think the boiler may have an expansion vessel too as it has a safety discharge pipe. The pipe from the red external vessel - if that connects to the other pipe it may have a tundish or be linked to the one earlier and if that’s dry then it’s likely the boiler one (if it’s has one).

 

[dilalio]

Your system pressure is low so you are losing water from it.

If you are capable, undo the nuts from the external EV and the boiler PRV, and pull pipework gently apart.

One of them will be wet.
This will be the one that is passing and will need sorting.