The melting time must be appropriate when connecting PPR pipes

The melting time of PPR pipes should be controlled within a reasonable range. The melting time is too short, the pipes and fittings are not heated enough, and the melting is not complete. It seems that the welding is good, but in fact it is probably a false welding, or even weak welding, and it is easy to leak when water is passed. The heat-melting time of the PPR pipe is too long, and the welding is very firm with a little force, but there is a drawback that the joint is easy to be too thick, which reduces the pipe diameter and reduces the water flow.