HOT WATER COMPLIANCE

PTR valve and drain line: the rules that fail jobs

The temperature and pressure relief valve is a safety device, and its drain line is where a lot of otherwise-clean hot water jobs come unstuck. Most of the trouble is not the valve, it is how the drain runs.

What the relief valve is for

On a storage hot water unit, the temperature and pressure relief valve vents water if temperature or pressure climbs too high, so the cylinder cannot become a hazard. It has to be the valve the manufacturer specifies for that unit, fitted in the right position, with the easing gear accessible and nothing capping or plugging the outlet.

The drain line rules that catch people out

The discharge line from the valve carries the most failures. As a rule it must be copper, the same size as the valve outlet, run with a continuous fall, kept within the length and direction-change limits, and terminate somewhere safe and visible so a discharge is noticed. No valves of any kind go in that line.

Common failures

• The outlet capped or plugged, which defeats the safety function entirely.
• The drain line run uphill or with a belly that holds water.
• Too many bends, or a run longer than allowed.
• Discharging into a concealed or unsafe spot where a fault would go unseen.

What to photograph for the record

• The valve in place, showing the easing gear and that the outlet is clear.
• The full drain line run, including its fall and its termination point.
• The manufacturer markings on the valve.

That set answers most of what an inspector or insurer would ask, and it is exactly what Elemetric captures as you finish the job.

Common questions

Can the PTR valve outlet be capped or plugged?

No. Capping or plugging the relief valve outlet defeats its safety function entirely and is an immediate fail. The outlet must discharge through the drain line to a safe point.

What is the relief valve drain line made of?

The discharge line is copper, the same size as the valve outlet, run with a continuous fall to a safe and visible termination, with no valves anywhere in it.

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.