It is tipping it down in Edinburgh at the moment. I can hear rain water hitting the inside of the flue pipe of my boiler. Is this a problem? It must be getting blown into the flue - my boiler is a modern combi one. Any central heating guys able to advise on this?
Can’t think of much I can do about it, mind. It’s currently off and I can make sure it stays off.
Is it PVC or metal?
If its PVC don’t worry about it. It’s a condensing boiler and it will run to a drain. Or, if it’s PVC you can put a 90 elbow on it, and a “street 45” on the 90. That will turn it slightly away from rain without turning it directly onto the roof. (flue gas is highly acidic)
If it’s a metal flue, than the top of the flue should have a “storm cap” on top of the flue, with a “storm collar” below the cap and above the roof.
The storm cap keeps water from getting into the flue, and then making it’s way into the burner chamber/ heat exchanger/
The storm collar keeps water from running down the exterior of the flue pipe and them into your attic through the roof penetration.
If it’s raining right now and you have no storm cap don’t fret. It’s not a good thing but one rainstorm will do little or no damage.
Over the longer term, however, a storm cap is needed, and you should get one soon.
thks raindog, it’s a pvc pipe straight out to the wall. I live in a flat, so the boiler is just right there against the outside wall - pipe can’t be more than 1m long. Anyhow, I’ll take yr advice and not worry about it 
One other thing…
If there is only 1 PVC pipe than don’t worry. (because that one pipe is an exhaust)
If there are 2 pipes…than one is a fresh air intake, and it’s not a good thing to have water in it.
The way to “test” this would be to fire the boiler and the one that is producing hot flue gases is the exhaust----and that is the one that won’t mind some rain water.