Drain off on Radiators and ground floor pipework

[VJ]

Perhaps one of the DIY or professional plumbers out there could answer the Question?

Why do French plumbers or (may be not all) NOT fit drain offs on base floor heating circuits especially where there may be three or four drops from the first floor?

I understand on a pressure heating circuit to release the presure on the boiler with the PRV manual control, but the leg with the ground floor circuit rads still has the rad water and the pipework water, albeit not pressurised.

There is no drain on either rad valves so it appears that the answer is to loosen the rad valves and catch the water (hell of a mess and fidley )

Try this with a 24 Column foot mounted radiator with bottom connections fed from above with 5 metres flow and return

Thank you