HOT WATER COMPLIANCE

Solar and wetback hot water: the compliance points

Solar and wetback systems still need everything an ordinary hot water unit needs, plus a few rules of their own. These are the extras that catch people out on a solar or solid-fuel job.

Collector and panel mounting

Solar collector mounting brackets carry a real load and sit in the weather for years, so they have to be a corrosion-resistant grade: stainless steel or hot-dip galvanised mild steel. Cheap brackets that rust out are both a failure and a safety problem on a roof.

Relief valve capacity

On a large or multi-collector solar system the temperature and pressure relief valve has to be sized for the combined output, not just dropped in as a standard domestic valve. Where the system can gain a lot of heat, the relief capacity is confirmed by calculation rather than assumed.

The wetback primary circuit

The usual rules still apply

Tempering to 50°C, the relief valve and its drain line, expansion control, insulation, and a safe tray where needed all still apply. Photograph the brackets, the relief valve and any capacity calc, and the primary circuit. Elemetric keeps it together.

Common questions

What grade are solar collector mounting brackets?

A corrosion-resistant grade: stainless steel or hot-dip galvanised mild steel, since they carry load and sit in the weather for years.

Can I put a valve on the wetback primary circuit?

No. There must be no valves of any kind on the flow or return between the heat source and the vessel, so a system still gaining heat is never closed off.

General information for licensed tradespeople, not legal or regulatory advice. The licensed plumber remains solely responsible for compliance. Refer to the current AS/NZS 3500 standards and the Building and Plumbing Commission (formerly the VBA) for authoritative requirements.