[Greenbuilding] Tank Water Heaters

[George J. Nesbitt]

Why do tank water heaters fail?
On average they last 13 years, why?
1. Lack of maintenance
2. Depleted Anode Rod. Made of magnesium (preferable), zinc, or aluminum 
(toxic element for humans), it corrodes easier so the steel tank 
doesn't. Should be checked and replaced periodically.
3. Electrolysis. Copper and brass fittings should not be use directly on 
the steel tank because the steel corrodes first. Use plastic lined steel 
nipples on all connections (many water heaters ship with them on the hot 
and cold taps).
4. Sediment Build Up. Heat caused minerals to deposit out. Higher 
temperatures cause more minerals to deposit out. More minerals in the 
water, more minerals deposit out. It collects on the bottom of the tank, 
reduces efficiency, increases temperatures, degrades the glass lining, 
reduces effectiveness of the anode rod, increase stress on tank. Use a 
curved dip tube (cold water inlet) to stir up sediment, and drain water 
from bottom of tank once a month at most.
5. High Temperature and Pressure. Higher temperature quicker rusting. 
High pressure (over 80 psi) greater movement, degrades glass lining, 
promotes rusting.
    This comes from "The Water Heater Workbook, a hands on guide to 
water heaters" by Larry & Suzanne Weingarten, ISBN 0-9630344-0-5


Keith Winston wrote:

>Do you really mean the tanks in your area fail due to scale formation, 
>or to simple deposits of sludge etc. in the tank? Also, the element gets 
>MUCH hotter than 120, as does the water in it's immediate vicinity. And 
>of course corrosion is yet another issue.
>  
>
>>Dr. Vasile may not be in such a hard water area.  Our water is so hard,
>>we use it to cut rocks (No kidding: http://web.umr.edu/%7Ewaterjet/) 
>>  
>>    
>>
>You're a goofball. That's a compliment.
>
>Keith
>  
>