I recently had my 4 year old water heater replaced because there was a slow leak in the bottom of the unit. It was still under warranty and I had it replaced with a new unit.
About ten minutes after the water was turned on, the temperature-pressure valve opened up and water started dripping. The plumbers were still here and they replaced the valve. The new valve leaked again.
I called a different plumber and had the inside pressure reducing valve changed as they thought there was too much water pressure in the house. That stopped the leaking until I started to use the dishwasher or clothes washer. Then the valve leaked again. I had the heater installer replace the valve twice more to no avail.
The valve only leaked when I used the appliances. The water pressure was checked and it was at 55 psi at the faucet. The valve is rated at 210 degrees and at 150 psi.
Now they are telling me that I need an expansion tank to solve the problem. I never had this problem before and I have lived here for years. I checked with the neighbors and they said they have not had this problem. This is a 40 gallon Craftmaster water heater with “Flameguard.”
Since the valve leaks after clothes washer or dishwasher use, hot water has recently been called for. The heater comes on to satisfy the demand for more hot water. In doing so, the pressure or temperature (water expands as it becomes warmer) causes the valve to leak.
The first thing to try is to lower the temperature control slightly. That may be enough to keep the valve from leaking.
If that doesn’t work, check the pressure-reducing valve you recently had installed. There are two types of valves: Those with a bypass that will allow for an open system and those without a bypass that maintain a closed plumbing system.
In an open system, if the pressure in the indoor plumbing lines increases beyond that which the reducing valve is set for, the valve will allow water to expand back toward the street and bypass the valve. Now, that will only work to your advantage if the street pressure is less. In some parts of Rochester, street pressure can be so high that indoor water pressure cannot overcome it.
In a closed system, the pressure reducing valve only works one way. Thus, any substantial increase in indoor water pressure may affect the pressure reducing valve on the water heater.
In some cases the expansion tank is the solution of last resort. So, first check what kind of pressure reducing valve you have and possibly change that. If the valve is the bypass type, I suspect you may have to install the expansion tank.
Water heaters manufactured today must have the “Flameguard” system that your heater has. This is basically a closed combustion system with a replaceable air filter that was designed to reduce the chances that gasoline or other combustible vapors don’t get into the heater’s combustion area. This change was mostly created to protect those heaters installed in the garage area of a house where automobiles, lawn mowers and gasoline are apt to be stored. This modification will add about $100 to the cost of the heater and will mean periodic changing of the air filter.