Low Hot Water pressure after burst pipe

[MontyMariner]

What a way to come onto a new forum!
Returned from holiday to find two burst pipes.

• One on inlet to hot water header tank
• T'other on outlet from hot water header (feed to shower cold water)

The central heating header tank was ok.
I have repaired the leaks and filled the header tank - so far so good!
I now find I have low pressure (flow) to hot water taps.
When I tried the central heating, the boiler (Vaillant ecoTEC plus 428) reported at various attempts to start:

• F22 - Dry Fire
• F23 - Water Shortage

Does the central heating boiler need bleeding?
If so where?
Is the main problem crud from the empty h/w tank got down the pipes and blocked the flow?
If so how do I go about flushing the pipes?

I know that I should get a plummer in, but at this time of year and heavy demand on services, I can't get one in the near future!

 

[Centralheatking]

It could be airlocked - if you have a mixer tap in kitchen block off common spout with thumb and cloth turn on hot and then cold water slowly - the mains pressure can remove the air locked hot.

If you have a hot and cold fill washing machine connect those accross - it does not take lots of pressure to free things up

centralheatking

 

[MontyMariner]

Thanks, I have X coupled H & C at washing machine and checked water flow into header tank from what I assume is the central heating over flow pipe.
Hot water tap pressure / flow now appears ok.
I have found a bleed valve at the top left of the Vaillant and bled that, no air came out just water.
Tried the central heating again, I now get:
S.98 - Flow-/Return-sensor check is running, demand (DHW or Heating) is blocked.