Central heating system wont drain

[MartinPatching]

Went to drain cental heating system to replace a lockshield and damaged 8mm pipe however all radiators drained except the two in the living room they remained fully pressurised even though the drain valve in the hallway was run dry as was the drain valve in the shower room on the opposite side of the hall wall. Replaced the pipe and valve but very confused as to why the only other two rads on the ground floor stayed pressurised and full of water, all trv and lockshields fully open on every rad during drain. Gravity fed system with water turned off anyone please advise??

 

[dcox]

Could these two rads be fed from dropped pipework?

 

[MartinPatching]

Could these two rads be fed from dropped pipework?

Dont know all radiator pipework dissappears into the walls i dont think so because the system jas been drained previously..

 

[jimbobby]

Have you opened any air bleed screws on upper rads to allow air in?

 

[Severntrent]

If you mean they are still full of water then the in and out pipework must rise above the top of the radiators to prevent them from draining as per dcox.

Dont know all radiator pipework dissappears into the walls i dont think so because the system jas been drained previously..

Previous drain may have been done i a different manner which enabled said radiators to have been syphoned out to some extent (enough to take the water below the bleed valves so they appear emptied?)