Locating boiler condensate discharge

[John]

I guess the OP also needs to think about the pressure relief piping route as well.

[DavidM]

Non combi boiler, open vented system, so no pressure relief pipe.

[DavidM]

Just out of curiosity, why change to 32mm after the first bit rather than stick to 21.5/22 until just before it goes outside?

[Ed Sirett]

That's the default instructions. Some models (specifically the Vaillant Eco tec family at least) allow the use of the smaller over-flow type plastic pipes.

This is because the condensate trap is syphonic and lets out the condensate in batches.

[Ed Sirett]

A soakaway is the absolute last resort, but an option nevertheless.

[John Stumbles]

The 21.5 out of the boiler has to discharge go into something bigger (as though it were a washing machine outlet hose going into a standpipe), not coupled together.

[Andrew Gabriel]

That probably depends on the boiler. Certainly my Keston expects 21.5 coupled together thoughout (increasing to

32mm only if it goes outside as a added protection against freezing).

Mine couples to a 32mm basin waste. I did include a bottle trap with integral AAV on the basin to prevent it emptying the U-trap in the Keston when you pull the basin plug, but there was no such requirement in the boiler instructions. Don't know if it would have been a problem without this.