Overflow discharge problem

Hello everyone
I have a question concerning thermalstore boilers including the pulsation. I run a McCarthy and Stone development and like 100s of others were fitted with all good intention with the Gledhill pulsacoil, but because of a hard water problem, those in my development are all leaking and the residents have been advised they need new boilers by Gledhill. They have all just passed the 10 year old mark and discharging rusty water from the base. Having some plumbing knowledge and I researched options for the residents for replacement boilers, as I am less than satisfied with Gledhill customer service and pricing. The problem with developments such as mine, is the restriction on running discharge pipes out through the wall and or accessing waste pipes for discharge through a tundish.
The fact that little old ladies have to fill their header tank above the boiler was dangerous from the start, but with all thermal store boilers, the cold water tank above the heater seems to be common. So plumbers attending my site, will where possible fit an unvented system and try and run the pressure relief valve into a safe discharge area, where they cant do that, they are then having to consider other options such a alternative thermal store boilers such as the ETS160 Electric Thermal Store by Advance Appliances Ltd or the 'Coral Aquanox Direct. Both of these have a cold water header tank, which looking at the specifications bother require an overflow through a tundish for discharge, but going back to my problem discharge to where? If access can not be gained to a waste pipe or externally because of building restrictions imposed by the landlord. So if one of the aforementioned thermal store boilers were fitted, what are the best options for discharge. I note that ETS160 states it can be fitted without an overflow - does that then need manual top-up like the pulsacoil - many thanks - Kevin

If it is manual fill then no overflow.
Have you checked what the Gledhill units are sitting on?
Most weigh a quarter of a ton when full roughly.
If not fully supported the bottom of the unit will drop. Thus causing internal leaks.
Also when the sites are built.
They flush the system perhaps with chlorinated water.
If that is used at the time to fill a unit, then trouble will occur.
There are many reasons why the units fail. Not always Gledhill's fault.
I have seen units replaced, which will fail in a few years due to the plinth not being strong enough to support the unit.
Gledhill now make a stainless steel unit which will replace the Pulsacoil 2000 and the Pulsacoil A class.
Pipe work much the same as in connections
The unit will need;
A supply (3 / 5 amp)
Off peak supply
On peak supply.
Mike