Water worker sounds like one of those Big Box brands. Chances are it's bad and needs replacing.
No, an expansion tank is not required.
expansion tank
Water expands when it is heated, this expansion increases the pressure. The bladder tank absorbs the extra pressure, protecting the hot water heater.
One possible reason for the temperature/pressure (tp) valve to start leaking may be from expansion of the water as it is being heated if there are check valves in the water system this is sometimes the culprit .In most water systems there is plenty of room for expansion in the distribution piping and service line and private well systems have a pressure tank that can absorb the expansion. You may have to add a small expansion tank to the water piping at the heater to solve this problem. hope this helps. Bob
Hook it up on the cold inlet side where you have room.
Yes they can go bad but are relatively easy to replace.
Many hot water heating systems with radiators need an expansion tank to operate efficiently. The fact you are in Concord NH is irrelevant.
because the steam that the water makes when it is being heated needs to go some where, if it deos not expand then it will explode.
Most Repairmen will charge a $50 service fee and usually around $75 an hour plus the cost of parts. If you need to replace your water heater that will cost between $700-$100 depending on size and brand.
Blow off valve faulty or expansion tank needed at water heater.
Generally this is caused by pressure being built up from the water getting hot in the hot water heater. By code you should have a hot water heater expansion tank on the cold water inlet of the water heater to absorb the added pressure. If this is your problem, the excessive pressure could possibly burst your water heater. The faucet stem or cartridge or washer may be loose or moving and blocking flow.
Check the temperature and pressure using two different gauges record both then either replace the T&P or install an expansion tank