Condensate disposal
"As previously mentioned some of the steam will condense back into a liquid. The amount of liquid will vary dependant on the boiler output, but to give you some idea of the amount the following calculation can be used:
Standard 3-bed house with a Y Plan and a 15KW (90%) efficient boiler
Gas input = 16.7KW @ 65% burn time = 10.85KW
Heating & DHW (winter) = 15190KW
DHW (summer) = 3580.5KW
Total 18770.5 KW
Time heating system <50°C = 30%
Amount of condense produced at 50°C = 1.35Ltrs/hr (20.83 cu.mtrs flue gasses/hr).
With approximately 1.35 litres of liquid to dispose of and the fact that the liquid is mildly acidic, the best position is to run the condense pipe internally into a sink or washing machine waste pipe.
However, if the condense pipe is run externally into a gulley, care must be taken to prevent the possibility of freezing. This can be achieved by ensuring that the boiler has an additional siphon kit fitted, allowing approximately half a litre of condense to discharge at any one time. It may also be prudent to increase the pipe size to a 35mm waste pipe. This would still allow a route to the drain if some of the condense did freeze in the pipe. Alternatively, you could insulate the pipe, but rodents generally destroy this and it looks unsightly.
Another option is to bury a soak away pipe in the garden and discharge the condense into this. It should be fitted a minimum of 500mm away from the house, with the holes pointing towards the garden. It should also be filled with lime chippings, as this will raise the pH level from acidic back to a more neutral level.
Finally, an installer could connect the condense pipe into a soil stack. However, remember that the regulations ask for a 75mm water trap and most boilers do not have a trap this size, so you will need to make a running trap (or similar). If the boiler is fitted below the drain level or the condense pipe length is greater than 3 metres you can install a condense pump. Ideal's Mexico HE has an enclosure for a condense pump and is already pre-wired to accept one.
It is currently acceptable to run the condense pipe into a rainwater system, but only if it is a combined rain water and foul system and of course not if it's connected to a rain water harvest system.
In short if the plumber just sticks it out the wall .... Your going have a little trouble !