Monthly: confirm the tank is full and the level indicator works and reads correctly; for pressure tanks, verify the gauge glass level, tank pressure within range, the air pressure switch operating at the compressor cut-in and cut-out settings, the low pressure alarm and the compressor or gas supply. Six-monthly: exercise the float valve and every level indicator. Yearly, all tanks: check joints, flanges and fittings for leaks, loose bolts and anchors, impact damage, foundation subsidence and cracks, external corrosion and internal corrosion as far as safely visible from the hatch, the hatch, ladder, roof stability and penetration sealing, vermin proofing, internal foreign objects, algae, vents and spinners, access, signs, gaskets and seals and the vortex inhibitor; lubricate the level indicator; confirm hard suction fittings suit the local fire authority. Drain, clean and refill once after the tank's first year in service and at 10-year intervals after that (divers or other underwater methods may be used with the tank manufacturer's agreement). Lined tanks: check fixings, discolouration, shrinkage, brittleness, cuts, tears and surface chalking above the waterline and flexibility, discolouration, elongation, bulging and leaks below it; when cleaning, leave at least 50 mm of water, avoid sharp tools and use suitable footwear; measure sludge depth to set the next clean; and study the base for undermining (minor hollows underpinned, major hollowing needs a geotechnical investigation). Rectangular panel tanks: inspect stays, bolts and brackets for corrosion, tightness, elongated holes and panel distortion. Pressure tanks: external inspection to AS/NZS 3788 and test of the low water level alarm.
The graph holds this control, the 0 it maps to, and the evidence behind each claim, over MCP and REST.