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I have a small bore system 10mm run from a combi boiler.
i intend on fitting a additional radiator to the system do i need to T into both the supply and return pipes and connect to the relevant ends of the new radiator.

Yes, that is correct, but you cannot "T" off a microbore pipe as it only has the capacity to run one radiator. You need to find the 15 or 22mm feed pipes.

it is to supply a new rad in the conservatory but all pipes are 10mm so does this mean this is not possible to do

[quote="ferret"]I have a small bore system 10mm run from a combi boiler.
i intend on fitting a additional radiator to the system do i need to T into both the supply and return pipes and connect to the relevant ends of the new radiator.[/quote]

If you use tees to add radiators to a system on a 10 mm supply you will starve the heat to one of the radiators. You will never have a full supply of heat to the radiator.

No system will be totally 10mm. The main feeds under the floor will always be 22mm. As they pass by each radiator, a tap off of 10mm will be made.

how will i do this other than T ing into current supply any suggestions

You need 22mmx22mmx10mm tee's or 22mm tee piece and then fit reducer to suit.

Basically all you need to do is tee into the 22mm flow and return - reduce down to 10mm pipe - radiator will work as good as the rest.

Make sure there's one flow and one return - if you accidentally tee into the same pipe twice - the radiator will not work.

htg

Track the 10mm pipes you refer to back to their point of origin, this is primary heating circuit. Hopefully this will be 22mm, or at worst 15mm. These are the pipes you should tee into (one flow & one return) and connect your supply for your new radiator.
If at all possible I would feed your new radiator with 15mm piping. 10mm & 8mm microbore are a cheap alternative to 15mm but are more susceptible to damage and blockages.