Lintel sizes underground

[Dad'n'lad]

Hi. Can anyone tell me if there is a recommended size of concrete lintels, for bridging over where my waste drainage passes through the courses below ground level.
I will be adding 150 to each end, and the opening will only be 110mm plus the 50mm all round for movement. ( plus maybe a little to keep to bond without cutting too much ).
It is 100/100/100 cavity wall, block inner, brick outer leaf.
Thanks

 

[noseall]

A 220mm opening will self arch unless the wall being built is less than two feet long, lol. 100mm x 65mm PCC lintel will be fine. We sometimes use a pair of 150 mm wide fellas* to prevent the cavity lean mix fill dropping on the pipe.

*We buy a longer one and chop it in half with the angle grinder.

 

[^woody^]

A concrete block will span it

 

[Dad'n'lad]

Perfect Boys. Thanks for the replies.