Home Inspection

The Role Of Expansion Tanks In Your Water Heating System

When a water heater is connected to a closed system, an expansion tank must be installed to prevent excessive pressure in the water. To help understand what this is all about, please read on.

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OPEN SYSTEMS
When a water heater fires up, the water in the tank expands. When this happens, where does the water go? Right back out the cold water inlet, all the way back to the water supply coming into the house. The municipal water supply for the house acts as a gigantic expansion tank… and nobody notices. This is illustrated in the diagram to the right.

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CLOSED SYSTEMS
What happens when a one-way valve, or check valve, gets installed on the water supply piping for the house? The water has nowhere to go. As the water heater heats the water, it expands, which builds up pressure. When the pressure builds up enough, the temperature and pressure relief valve on the water heater simply does its job. It relieves the excess pressure by leaking a little bit of water.

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This doesn’t happen every time that a pressure reducing valve or check valve is installed, but there may be other problems that show up in the house, such as the toilet fill valves randomly re-filling toilets, or faucets chronically dripping.

In Texas, it’s rare for a check valve to be installed on the water supply line for the house, but it’s fairly common to have a pressure regulator installed. The problem that these regulators can create is that they will act as a check valve; they’ll allow water into the home, but they won’t allow water back out. This creates what is called a ‘closed system’.

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EXPANSION TANKS
When a closed system exists on the water distribution piping in a home, an expansion tank needs to be installed somewhere on the plumbing system. This is a fairly simple and straightforward fix; an expansion tank uses an air bladder which is compressible which gives the water somewhere to go when it expands, and the temperature and pressure relief valve on the water heater will stop causing problems.

REQUIRED OR JUST A GOOD IDEA?
As of 2018, the International Plumbing Code 607.3 requires an expansion control device whenever a check valve or pressure reducing valve is used in the water supply.

Where a storage water heater is supplied with cold water that passes through a check valve, pressure reducing valve or backflow preventer, a thermal expansion tank shall be connected to the water heater cold water supply pipe at a point that is downstream of all check valves, pressure reducing valves and backflow preventers. Thermal expansiontanks shall be sized in accordance with the tank manufacturer's instructions and shall be sized such that the pressurein the water distribution system shall not exceed that required by Section 604.8.

About Ground Fault Circuit Interrupters (GFCIs)

What is a GFCI: The ground-fault circuit interrupter, or GFCI, is a fast-acting circuit breaker designed to shut off electric power in the event of a ground-fault within as little as 1/40 of a second. It works by comparing the amount of current going to and returning from equipment along the circuit conductors. The GFCI will “sense” the difference in the amount of electricity flowing into the circuit to that flowing out, even in amounts of current as small as 4 or 5 milliamps.

Purpose: A ground fault circuit interrupter can help prevent electrocution. If a person’s body starts to receive a shock, the GFCI senses this and cuts off the power before he/she can get injured.

Where should GFCIs be used: GFCIs are generally installed where electrical circuits may accidentally come into contact with water. They are most often found in kitchens, bath rooms and laundry rooms, or even out-doors or in the garage where electric power tools might be used.

How should a GFCI be tested: Whether you have a receptacle or circuit breaker GFCI, pushing the TEST button should turn off the power to the circuit. For the receptacle-type GFCI, pushing the TEST button should cause the RESET button to pop up. (Remember to push the RESET button to re-establish power and protection.) For the circuit breaker-type GFCI, pushing the TEST button should cause the handle to move to the tripped position. (Remember to reset the handle to re-establish power and protection.)

When should GFCIs be tested: GFCIs should be checked monthly to determine if they are operating properly. A portable GFCI should be used out-of-doors with various electrical power tools (i.e., drills, mowers, trimmers) and should be tested before each use!


Read more about GFCIs from InterNACHI here https://www.nachi.org/gfci.htm