Is this right?

[itsnewtome]

Hi
I don't know anything about rainwater harvesting so am curious as I've been working at a house with a system. To me it seems to be wrong and doesn't seem to serve any purpose- I may be wrong.
The system is like this.

Storage tank above ground on concrete plinth.
House has 4 down pipes + neighbours rear roof going into system.
All 4 down pipes connect into a 4" soil pipe which is buried around the outside of house.
It then travels across the garden slightly uphill where it pops out of the ground and feeds into the top of the tank.
Tank today was full and there was water in the downpipes up to head height (same level as top of tank)Approx 2m head
No pipework back to house can be seen- I dont think there is any.
Overflow pipe is a piece of guttering laid into some shrubs.
Surely this isn't right is it?

[odbob]

The tank is full so it's obviously working but yes curious as to how they have prevented leakage from the down pipes and particularly the 4 inch pipe.
The idea is sound enough IE to use the head of water to serve the tank, and infact mine works in a similar manner, but that said, mine is constructed of welded upvc pipework extending from all points around house at gutter level, all joining up prior to entering a sand filter and then on to the u/g tank. (I use the head pressure to force the rain water through the sand filter.
As for the outlet pipe, it is possible that this is simply buried out of site and only appears within the house, easiest I suppose is to ask the owners