problems with overflow on header tanks

[MikeF00]

Hello, i recently rerouted some plastic overflow pipes from both header tanks in my attic to the outside through an external wall. When i came to test them for leaks (by holding down the ball float) and trying to allow water to flow down the newly rerouted pipes , nothing happened and water did not flow down the pipes? Is this due to some weird air pressure trap(think its called hydrostatic pressure) in the pipe work?. This wasn't a problem when the pipe was routed the other way.

The overflow pipe in the tank(s) does have a 90 deg elbow on it and points directly into the water. Although i have not changed this from last time. Both tanks have the same configuration in them

Any suggestions?

 

[Simon F]

Hello Mike and :welcome:
what is the fall on the new pipes?
what size overflow pipe?
what length of run?
have you tried blowing down the pipe? there could be a blocckage

 

[AWheating]

first check for a blockage, you may have picked up some insulation when routing through walls etc.... what fall do you have on the pipework?