Why do some overflow pipes have a 45 degree cut

[RhinoFog]

Hi

I have installed a header tank in the loft for a rain water harvesting system and as per design it has a 40mm overflow pipe to the outside.

I see that overflow pipes sometimes have a 45 degree angle cut on the outlet end.

What is the purpose of that cut and do I need to make one or can it be left stright?

The second question is whether I should put some form of grill, self sealing waste or one way valve on the pipe. I am just wondering if at 40mm there is a chance that flying insects/wasps might find it as a way in to the loft. Thoughts?

Thank you for your help.

 

[bernardgreen]

With the 45°cut water accumulates at the point, overcomes surface tension and drips off. Without the 45° cut the water spreads around the end of the pipe and it takes longer for the surface tension to be overcome. In freezing conditions the pipe with a 45° cut end will take longer to become blocked by ice,

 

[Madrab]

The second question is whether I should put some form of grill, self sealing waste or one way valve on the pipe. I am just wondering if at 40mm there is a chance that flying insects/wasps might find it as a way in to the loft. Thoughts?

You need a bylaw 30 kit, that's designed to stop insect etc for getting in.

 

[RhinoFog]

With the 45°cut water accumulates at the point, overcomes surface tension and drips off. Without the 45° cut the water spreads around the end of the pipe and it takes longer for the surface tension to be overcome. In freezing conditions the pipe with a 45° cut end will take longer to become blocked by ice,

Thank you Bernard.

A follow on question: should the 45°cut be upwards or downwards or does it not matter?