How Important is a T&P Valve in a Water Heater System?

March 6, 2019

There are two dangerous energy types locked inside a water heating system. Thermal energy comes first because this is the equipment’s raison d’etre, the generation of hot, steamy water. The second energy type, which holds water at bay, is pressure. Now, by employing a little logical reasoning, we can figure out what T&P valves regulate. That job, if it isn’t already clear, is to unload dangerously high temperatures and/or pressures.

Closed System Dangers

Hot water comes from a storage tank or it’s heated directly by a gas flame or electric element. As long as the system taps and outlets remain closed, the water circulates in a closed loop. It’s in a kind of holding pattern, with the closed channel waiting for a demand source. Preinstalled and welded to the side of this or any water heater, a T&P valve fades into the background. Its drain pipe drops down to a drain in the floor, so there’s a safe pathway for a hot and pressurized stream to discharge. Other than those features, the fitting goes mostly unnoticed. That’s not a good thing, not for a system safeguard. Remember, this is a safety device, one that’s designed to unload dangerous energies.

A T&P Valve Maintenance Check

Because the fitting goes unnoticed, and because it doesn’t operate unless a dangerous fault condition exists, the valve can become so stiff that it no longer functions properly. Also, and this problem could cause valve stiffness, too, liquid-suspended debris may make its way into the valve mechanism, where it then proceeds to jam the moving parts. In short, there’s no way to tell if that fitting is operational unless it’s tested from time-to-time. It’s probably going to work just fine, just as the hot water system reaches 99°C and/or 150-PSI, but such assumptions cannot be made, not if a safety factor is to be assured. No worries, a lift-control trigger tests the valve. Importantly, a high-pressure, high-temperature stream of water will discharge energetically when that valve is manually triggered.

An incautiously applied test could result in a nasty scald. Leave this job to the experts. Likewise, if it’s time for a system flush, call out a service engineer. The tech will lift the valve tab, trigger the discharge, and then the hot water system will flush. That’s a good way to free that valve-clogging debris, by the way. And, before even approaching the equipment, do remember that this is a potentially dangerous appliance. It’s designed by knowledgeable engineers, so it’ll channel and regulate the high pressures and temperatures. However, as a last line of defence, a T&P valve must function. If it doesn’t discharge those overly energized fluids, perhaps because it’s fallen into disrepair or is clogged, then a catastrophic burst hazard is likely imminent.

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