What are the likely causes of water discharge from the pressure release valve on a forced water boiler heat system? Why is it a bad thing?
Strainer clogged, too much condensate, ph off, too hot…
The pressure reducing or fill valve for a boiler is set to only allow 12 psi in to the boiler. If this valve fails it will allow the pressure in the boiler to reach 30 psi or higher. causing the relief valve to leak. if your gauge goes over 30 psi and the relief valve does not leak, turn the boiler off. A plumber may be needed at that point
The use of a pressure valve that is not rated for the appliance or a damaged expansion tank could result in a rupture within the system.
There are three reasons a T&P valve opens. Temperature, pressure, or a faulty valve
To high a temp, pressure, bad expansion tank, bad / faulty aquastat relay, pinhole in a tankless system.
The system is building too much pressure or in the case of the pinhole it loses pressure and the pressure from the home may seep into the system.
Kens Answer is MOST complete… Looking for faulty valve or expansion tank, excess pressure.
The simple answer… too much pressure, or failure of the valve. What caused it? Could be a long list of things.