Self cutting drain valve for rad pipework

[zanwan]

I've drained down my central heating as much as was possible however i could only get down as far as the just below the boiler as the muppet who fitted the central heating system has fitted no drain valve to any of the ground floor rads.

I am considering a self cutitng drain valve to drain the system fully, by fitting this to one of the lowest points on the central heating system. However i've put sentinel 400 sludge remover in the system and will be draining this down in 3 weeks time. Now my concern is the connection on the self cutitng drain valve, where it cuts into the pipe looks very small. Now will this hole allow any sludge, debri through?

 

[Gasguru]

Forget it.

Some of them leave the cut out disc in the pipe. The hole size is too small...designed for mains pressure. And long term the O ring seal won't take the heat.

Just drain off a small rad, swivel the valve round and connect on a hose and tee in proper drain-offs.