The atmospheric tank is slightly inclined forwards (because garage floor was poured to drain) so water is slightly deeper at front. There are 2 low level float switches, one at front and one at rear. Rearmost one trips first as water is pumped out because of slope. When it does it shuts off pump (and lights Tank Low lamp). When RO unit supplies enough water to reset float it signals a 6 minute timer to start. At timeout the pump starts again. Tank Low lamp stays lit until end of timeout. If rear float or timer fails and pump keeps running front float will eventually trip. This latches pump circuit off (and illuminates Latch lamp) until manually reset (Reset Button). Two high level floats are in series with RO unit control. If either opens RO unit AC is switched off.

Pump and RO unit can be switched off (center) on (down) or put under control of the float switches (up). Pump and RO unit AC is furnished through SSR's in control box which also contains EMI filters for pump and RO unit as pump (diaphragm type) puts spikes of over 1 kV on line. This interferes with TDS meter on RO unit.