"Why would anyone need an expansion tank?"
Water is incompressible. Unlike air, it's impossible to squeeze any quantity of water into a smaller volume.
Where that matters is in "closed" water systems such as a water heater with a check valve (pressure regulator and the like)
ahead of the heater. When the water gets heated it expands and that extra volume has to go someplace. Without an expansion
tank the pressure could rise to a dangerous level in a closed system. A diaphragm type of expansion tank (such as what we sell)
is a pressure vessel that contains a flexible membrane totally separating the water from a captive volume of air. Air compresses
and as the water temperature rises, creating extra pressure/space, the air in the vessel accommodates that increase. Thereby preventing
a potentially dangerous pressure rise.
"Why is there a hole near the top of your diptubes?"
The reason for the hole is to break siphonage effect when the water is shut off and there is a drain down situation (caused by
such things as a valve or a leak that is below the waterheater). A common example would be in a mobile home water heater, where the water supply
is nearly almost always under the floor. If the water gets shutoff (for whatever reason), without that hole, the diptube could possibly backsiphon
(empty most of the water and drain it to the level of the inlet on the coldwater diptube),
burning up the elements or possibly allowing the gas burners to damage the near empty water heater. Bottom line, it's for safety.
"I have a rattling sound coming from my water heater when the hot water is running?"
Check to see if you have check valve type nipples installed on the top of your water heater.
They generally look like ordinary galvanized nipples and so sometimes it is
hard to tell if they are installed. Some water heaters come with them. They are
a great idea because they can save some energy, but they also can be very annoying.
"I am looking for 120V water heater I can install under my kitchen sink. I
need one that will provide about one sink-full of hot water on demand (It
currently takes about 60-80 seconds to get hot water to the sink). Will your above undercounter water heaters work for me?"
Yes, the 2.5 gallon "should" just be "perfect" for your situation. It holds 2 1/2 gallons and when mixed with cold water
would give you over 4 gallons of mixed warm water which is plenty for almost all residential sinks.
We like to recommend these for under the kitchen sink and for your "cold" inlet you can use your hot water supply.
