pou hot water tank; where is the air coming from?
Hey Guys,
I’m hoping you can help me understand a mystery. I’ve installed a small tank electric water heater in the vanity of a 2nd story bath. The tank serves to provide hot water to a double bowl sink arrangement. The goal was to solve having to wait for minutes for the hot water to reach the sinks which are at the far reach of the existing plumbing line. The diagram illustrates how we put it in. The goal was achieved. Hot water is now nearly instant as it only travels a few inches to one of the sink and about 2 feet to the other bowl.
What is troubling is that air is getting into the tank lines. So when you crack the hot water spigot…Pow, Pow, Pow…you are surprised with a rush of air following a brief flow of water. After a few seconds the air is replaced with supply water and it runs fine. If the line is not used for a few days the amount of air is increased. More, longer and louder pows as the air purges. My theory is that as the tank warms the water it expands and pushes some back into the supply line. Once it reaches temp the water cools slightly but rather than moving back into the tank it leave a void some how. Any ideas how to correct?
Replies
HW tank
You might check the temp. of the water. That might be a little steam that is blowing the water out.
When you heat water you increase the solubility of solids in the water, but decrease the solubility of gasses. This means that much of the gas dissolved in the cold water coming into the house is "driven out" as it heats, producing gas in the water heater(s). In this case I suspect that what's happening is not that this water heater is itself driving off all that much gas, but rather the gas that's "liberated" in the main WH is working its way up through the pipes and ends up this heater.
Your "cooling water contracts" scenario would only be possible if there was a valve between the two heaters that was being shut off intermittently.