Lots of Water from my T.P.R.

[RayW]

I heard a whistling noise come from down stairs and when I looked the floor was totally soaked from water draining from the temp.and pressure relief valve. IT is still leaking a little bit but steady. I released the valve and tons of water comes out. Any suggestions would be great, Thanks RayW

[LazyPup]

The first thing you must determine is what caused the Temperature & Pressure Relief valve to open.

Technically there are three conditions that can cause the valve to open.

1. TEMPERATURE: T&P valves are factory preset to release if the water temperature exceeds 210degF. It is now customary to operate water heaters at 120 to 125degF so the odds of the tanks overheating are very slim, however it is possible if there is a problem with the control thermostat. If the T&P valve is releasing as a result of overheating you should turn off the fuel supply (Gas valve or electrical circuit breaker) to the heater and have it checked immediately.

2. PRESSURE: T&P valves are factory preset to release if the internal pressure exceeds 150psi. The plumbing codes limit the potable water distribution pressure to not more than 85psi. In instances where the supply pressure exceeds 85psi we are required to install a Pressure Reducing Valve (PRV) at the main water shutoff and we must install an expansion tank above the water heater.

3. The third possible cause is water expansion. Water reaches maximum density at 39degF and when either cooled below or heated above that temp the water expands. This explains why a pipe will burst when frozen or could possibly blow if overheated to a pressure exceeding the maximum limits. Normally in summer the incoming water will be about 55degF which is the average geothermal temperature of the soil, however in winter as frost permeates the ground it is not uncommon for water temps to fall to the mid 30 to mid 40degF range. This explains why expansion problems are normally more prevalent in winter then in summer.

Under normal circumstances there is enough expansion room in the water hammer arrestors to absorb the expansion and in a worst case the excess volume can backflow out the supply line to the municipal main, however, if the supply line happens to have a backflow preventer (check valve) and if the water hammer arrestors happen to be saturated there is no longer suffient space in the system to absorb the increased volume as the water is heated in the water heater.

If the problem is associated with saturated water hammer arrestors you would normally also experience a bit of water hammer (pipes clanking) whenever a fast acting valve is closed. Fortunately that problem can usually be resolved very easily.

First turn the main water shutoff valve off, then open both a hot and cold water faucett at a high point in the system (normally the bathroom lavatory faucetts) then drain the whole house water distribution system from a low point, typically a laundry sink in the basement or an outside hose bibb. (You do not need to drain the water heater at this time).

Once the system is drained close the faucett at the low point and open the main water shutoff valve to refill the piping. During the refilling process air in the pipes will be trapped in the water hammer arrestors restoring them to full charge. Watch the water flow at the high point faucetts. You should expect some hissing and sputtering as the excess air in the pipes bleeds out. Once the faucett has a full water flow, close that faucett, then go throughout the house and open all the faucetts to bleed off any excess air, again closing the faucett once full flow has been restored.

Quite often during the draining and refilling process minor bits of scale or debris will be dislodged into the piping system and you may need to clean the aereator screens on the kitchen and lavatory faucetts within a day or so. This is to be expected and is no cause for alarm.

Under normal circumstances mineral scale will often build up on the inside of the water heater T&P valve and once the valve has released some of the mineral scale may become lodged in the valve seat preventing the valve from fully closing again. Normally you can manually lift the valve by means of the manual test handle, then allow it to snap back in place and that should flush the debris and permit the valve to reseat. If it does not reseat after two or three attempts consider replacing the T&P vavle.