pumped shower issue (needs second shower on to start the flow)

Hi guys,

friend of mine having issues with new plumbing (old pipework utilised i beleive) for pumped showers upstairs.

The pump seems to work fine, located at the hot cylinder same floor as showers. the main shower fires the pump when the flow is turned on fine but when the ensuite shower is turned on nothing happens. No flow, no pump.....buut if you turn on the main shower to get it flowing the ensuite shower then starts flowing fine. And for a period of time afterwards (about 30minutes) the ensuite shower will turn on without needing the main shower on. But after that it will resort back to the same issue.

its very strange. Anyone seen anything like this before. Im guessing as a bit of a novice that opening the shower valve triggers a pressure drop that triggers the pump to flow. Why would the ensuite not trigger the pump? is it possible an airlock repeatedl enters the pipework somehow of what might be causing this quirk?

Opinions much appreciated

 

Is ensuite on same floor as other shower and distance from pump causing low pressure to activate pump maybe.

 

Same floor similar distance. The head pressure should be quite similar for both showers

thinking maybe the non return valve in the shower unit is not compatible with the low pressure in the system ?

 

That is possible. Most items are pressure related.