Adding a towel radiator to bathroom

[dilalio]

Is it safe to assume if a rad valve is unidirectional it will be clearly indicated as such.

Gus, he's referring to TRVs in his post not lockshields/manual valves, so you're good to go on either side.

Edit: quality, modern TRVs are biflow.

 

[dilalio]

I may regret asking this but what is a bypass and why do you need at least one radiator as a bypass?

We do have a combi boiler btw.

To provide a large surface area to dissipate heat from the circuit in the event that all TRVs shut down flow through all the other rads. Your combi should have an internal bypass but it is normal practice to utilise at least one rad on the circuit to facilitate this. Usually it's rads in washrooms and the rad that's in the same room as the roomstat.