Axel,
Yes we will !!!
Well the Techflow Service Engineer visited. He couldn't fault the installation and plumbing. He concluded that it must be the pump and fitted a brand new Twin Turbo 3 Negative Head pump to replace the existing Turbo 2. Result.... the same problem existed but now the pump kept running on and every 10 seconds or so would hesitate ie. momentarily shut off then on again.
Despite adjusting the reed switches, and in fact removing them completely, the pump ran on !!! If both the pump outlet isolating valves were closed, the pump ran on when all outlets (taps) were closed. Occasionally. if you opened and closed a tap, the pump would shut off. We also continued to get the hesitation.
The Techflow engineer made some other checks on the pump and he concluded there was something wrong with the PC Control Board in the pump. (This was a new pump !!??) Seemed a hell of a coincidence.
Anyway, as Techflow are now owned by Stuart Turner Pumps, the Techflow engineer called Head Office and arranged for a new Stuart Turner Monsoon Universal Twin 3.0 Bar pump to be despatched to replace the Techflow pump.
I removed the Techflow pump on 8 Feb and fitted the Monsoon and the system is working absolutely fine !!!!
I have made no changes to the plumbing except for minor pipework changes to marry up with the Monsoon inlets and outlets. I took the opportunity to mount the pump on a piece of concrete paving slab. The pump is much quieter than the Techflow. (The concrete slab has made quite a bit of difference.)
Conclusion: The original Techflow pump worked for a year before exhibiting problems. The replacement Techflow pump - just bad luck !!
I certainly would only use a Stuart Turner pump in future. Since Techflow are now owned by Stuart Turner maybe the product range will be rationalised, and all the best design features of the Stuart Turner pumps will be integrated into any new pump designs.
Hope that closes the whole saga now !!!