10/30/2025
Does your water heater need a thermal expansion tank on a closed loop? Let’s get into this. The simple answer is yes your water heater needs to have a thermal expansion tank and is mandated in the manufacturers specifications being part of a full install. The reason goes into the science of water and is one of the only substances that cannot be compressed. Water expands when heated because the added energy causes its molecules to move faster and further apart, increasing the overall volume. As molecules gain kinetic energy, they break free from intermolecular attractions and push against each other, creating more space between them. This process continues until it reaches a higher temperature where another effect dominates, but is a common characteristic of liquids and solids at temperatures above a specific point. A 40-gallon water heater will produce about a half-gallon of thermal expansion when the water is heated from a typical starting temperature to a common thermostat setting . This extra half-gallon of volume needs to go somewhere, and if the system is closed, it will create excessive pressure, if left unprotected it will activate the temperature pressure relief valve to discharge. The T&P valve as we call is is one of the safety features on your water heater designed to protect the unit from explosion. Also remember if your water heater expansion is present this subjects the unit to a staggering pressure of a 150psi, Keep in mind all your plumbing is connected so no not only your heater is extremely high but also the rest of your plumbing system is subjected to that high pressure and often times causes premature failure of appliances,pipes and valves tied into the system. So if you observe your T&P discharging, let the licensed professionals at NPTP install a thermal expansion tank to provide protection of your homes plumbing. See ya next time on “ Let’s get into this”.