How direct and indirect systems get cold water to each outlet.
Both systems start at the incoming main and stop tap, but they distribute cold water differently.
In a direct system, the rising main feeds every cold outlet, so the kitchen tap, basin, bath and WC all run at mains pressure.
In an indirect system, the mains feeds only the kitchen tap — kept on the mains for wholesome drinking water — and a cold water storage cistern in the loft. The stored water then feeds the basin, bath, WC and the cold feed to the hot water cylinder by gravity.
Use the comparison to remember the trade-off: direct is simpler and at mains pressure throughout; indirect provides stored water and a lower, gravity-fed pressure to most outlets, while keeping the kitchen drinking tap on the mains.