Combi air-lock question

[dal5band]

We re-routed the hotwater run from the combi to the bathroom so it is more direct but now there appears to be a flow problem. When first turned on, the hot tap gushes but soon slows down visibly.
The cold in and the hot out are virtically below the boiler, about 6 feet straight down - the pipes run under the ground floor before coming up near the kitchen. The cold pressure is fine.

Could this reduced flow be caused by an air bubble trapped in the H/W part of the boiler or does the mains normally blast any air through?

 

[gas4you]

Sounds more like some debris has got in the hot pipe run, also check inlet filter on combi

 

[dal5band]

Thanks , gas4you you were right. After a day or two the upstairs H/W cleared but the kitchen hot was still weak. Off came the first joint under the kitchen H/W tap with a bowel under the open pipe. put my hand over the end of the mixer tap and turned on the cold - out came some clinker from the breeze blocks in the wall where we had put the new pipe run through.

Honest we did tape up the end of the pipe before pushing it through the wall but obviously the dirt had snuk into the pipe already from the drilling !