The baths & sinks etc should drain via 32 &40mm pipe into a holding tank
usually buried in the ground you then install small bore pipework via a pump to supply toilet flushing etc - it sounds like you have not thought about the low level storage tank!!
Boiler man your correct mate, i have researched the system and it is how you say.
Loft tank and underground tank all fed by the 32 and 40 mm waste.
Re think needed and thanks for yr help, much appreciated
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