Water Expansion Tank Location

[Aromaz]

In a setup with a water heater and seperate storage tank with a floor mounted circulater pump, where in the loop should the line to an expansion tank be tapped in? Right now I have it in the suction line between the tank and pump. Somehow this doesn't seem right. Any ideas? Thanks.

[Anonymous]

OK, I'll bite - what is the purpose of the expansion tank?

[pete f]

Extraplay
The expansion tank is a holding tank for hot water for busy periods.
At least I am assuming, I don't use them.

Most hot water circulators are set up to run hot water thru the lines at all times, and back to the main tank. Though this in theory is great, in practical terms it may not be such a bright idea, unless you have a huge mat. What happens then is the first customer who washes on hot water may get 1/2 tub of cold to warming water, then hot. Once the hot water is in the line, here in Florida it sort of stays there, so the next person gets even more hot water. If the heaters and washer are very far apart, then the reciric may be needed. I use tankless in two mats, and have no expansion or recirc. I have yet to hear a complaint. But then again I am unattended and not there to listen. Really, customers leave note about stuff they are unhappy with. Hot water has not been an issue. Tankless can fire up very hot water quick, so when it hits the washers it is steaming.
As to the original post, it seems the pump just keeps the storage tank full of hot water.

[Anonymous]

Don't think so -- that is what a storage tank is. An expansion tank is a small tank about the size of a 5 gallons bucket with a diaphragm in it and air pressure on one side. The question I have is exactly what does it do and why do you or don't you need one. I have seen hot water systems both with and without them and am wondering why you need them and what they do for you.

[Aromaz]

When you heat water in naturally expands. The higher the temp, the more it expands. As it heat up, if a fawcett is open or a washer or washers are filling, no problem. In places like Florida you have to have backflow preventers on the main water line coming in to the building. If no water is running and a backflow is in place, you have a closed system and the water pressure builds up and pops the relief valves on the heater and/or tank. An expansion tank has a diaphragm and compressed air to allow the water to expand.

[Anonymous]

OK, that makes sense, but why don't I need one on my hotwater heater at home then? I have one at the mat now with my high eff water heater, but with the old water heater there was not one. I know of many mats that don't have them and have no problems. What dictates if you need one or not?

[Rondo]

http://www.wattsreg.com/default.htm?/thermalexpansion/

It can't be in the hot water loop, it installs in the cold water inlet for the boiler. It has a tire valve in the bottom, the pressure should match your incoming water pressure.

[dzender]

The expansion tank is designed to take any vacuum out of the water line so any hiccup does not blow your backflow preventer.

On my set-up, the expansion tank is mounted on the inlet water line right after the backflow preventer and right before going into the boilers. The boilers are piggybacked together and the outlet is fed into two storage tanks where the circulation pump keeps the flow going through the tanks and boilers.

[Aromaz]

dzender,
The loop returning from the tank joins together with the main cold line before entering the boiler. Right? Is your expansion tank tapped into the cold line before or after in connects to the loop?

[laundryboy]

The expansion tank is to prevent "water hammer" from harming your delicate components on the water system. You can cause water hammer by opening a valve full (sink water fauset will work) and then shutting VERY fast. If the water is flowing fast enough (by volume), stopping the flow abruptly causes an increase in pressure throught your water line. When this happens repeatedly, it will stress all components on the system like washer valves and heat exchangers.

The diaphram in the small tank absorbs this increased pressure and stabalizes the system (like a shock absorber). Oddly, the larger your water line in, the less hammer you will experience. A one inch line will "knock" considerably more than a 3 inch line. Older laundries usually have large lines (all those tops), thus few had expansion tanks. If you are adding a high efficiency heater (mico tubes) definatly add the tank. The cost is minimal ($80.00) compared to the reduced stress on your components.

[DuboisLaundry]

my expansion tank is to prevent blowing the relief valves on the EVO99 boiler and the storage tank. It is located between the pressure regulator from the cold water supply and the return line from the storage tank to the boiler inlet.