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A Brief History of Water Heaters: Part I

“Once Upon a Time…water heaters, all water heaters, used to last at least a dozen years, and often even twice that. And we never, ever use to see things like those little expansion tanks, earthquake straps, pans, or stands on water heaters. What happened? Why have these things changed? Is it just more code bureaucracy? Is it cheaper, lower manufacturing standards? What’s happened?”

When I started plumbing many decades ago, most water heaters were the standard 40, 52, or 66-gallon tank water heaters, and it wasn’t unusual to change a leaking water heater that was 15 to 25 years old. Many of the components now required by code just didn’t used to be installed. You never saw them. Things seemed to work fine and last a long time. What’s happened?

In this and the next one or two articles I’ll share a brief history of water heaters and what’s behind some of the changes that have been made…

Expansion Tanks

Many (30+) years ago, everyone living in any city in North America had either a very basic water meter out at the street, or no water meter at all and just an in-ground shut off. If you wanted a sink, toilet, or water heater, there were very few places to get anything like that except at a plumbing shop. For a long time even local hardware stores didn’t have plumbing fixtures; just a few toilet-repair parts and faucet washers.

Then in the 80’s the first ‘big-box home center’ stores started on the East Coast and moved west, and in 20- years they were everywhere and the DIY (do it yourself) market exploded. Everything anyone wanted for home improvement, including all plumbing fixtures and supplies, was readily available, and in many places there were even quick little workshops to show you how easy it is to do things yourself. So, you could avoid those expensive tradespeople and even those pesky government codes if you wanted to.

Interestingly, at about the same time, water purveyors (the people responsible for city/county water supplies), and back-flow device testers started noticing a huge increase in ‘cross-connection’ events, especially in residential areas. A cross-connection event means that the potable drinking water system has been contaminated somehow, and it soon became apparent that the increase in these events was likely related to all the DIY projects happening everywhere. So, to protect the city/county water supplies, most of the public water systems started to install new water meters that had ‘check valves’ in them ( the old ones didn’t). With these new water meters, once the water went through it, it couldn’t go backwards, or ‘back flow’ into the potable water supply. This completely changed the dynamics of every water system that was served by these new water meters.

Why? Mainly because in the morning, when everyone showers and uses a lot of hot water, it has to be replaced with fresh, cold water. And when cold 45-degree or 50-degree water is heated to 120 degrees, the water physically expands and grows significantly; 40 gallons becomes 40.7 gallons, 50 gallons becomes 50.8 gallons etc. And if everyone has gone to work or school and no one uses any water, where does that ‘extra’ ½ to ¾ gallons of water go? Well, it used to just go backwards out into the city main through the old water meters, but if the water meter is newer and has check valves in it, it can’t. And if it can’t go backwards, (or into a properly installed expansion tank), the pressure increases hugely on the water system until the water heater’s relief valve starts to leak or ‘pop off’ and relieve the pressure (assuming the relief valve was still working properly). By that time the big pressure increase had already started to do its damage on the different parts of the water system. High pressure like that is hard on all the water valves, and every time there is a big pressure increase, it can cause the sides of the water heater to bulge or swell slightly, just enough to crack the ‘glass lining’ that protects the inside of the steel tank on the water heater. Then, thousands of tiny cracks in the glass lining + fresh water + steel = corrosion = leaks. Leaks much, much sooner…years sooner…than necessary or normal for that tank.

This is such a basic, fundamental issue, that every single manufacturer of water heaters voids the unit’s warranty if its installation doesn’t include (among other things) a properly installed expansion tank and/or relief valve that is maintained (checked) annually.

When installed, the expansion tank should be ‘tuned’ to that specific system. Expansion tanks have an air chamber and a water chamber, and the pressure of both needs to be about the same. The chambers are separated by a butyl/rubber bladder so the water and air don’t touch, because that would cause the water to absorb the air bit by bit, and over a year or two the ‘balance’ would be gone. Imagine what would happen to the room in the air chamber if the water pressure was 80 PSI and the air pressure was 30 PSI; the higher water pressure would push the bladder way over and greatly reduce the room for expansion into the air chamber, when heated, expanded water needed a place to go to.

Some manufacturers of expansion tanks claim that their ‘pre-charge’ of 40 PSI or 50 PSI is close enough to most of the water pressures on most water systems. Well, perhaps so, but in our company it’s simply lazy to not be sure and balance the air side to the water pressure. Also, we recommend that it be checked annually with the water heater’s annual maintenance, because you never know what will happen in the local neighborhood’s water pressure or if the bladder has failed prematurely.

Next month, join us to explore some of the other changes that we see nowadays on water heaters

Bruce Davis, Sr.
President, Director of Education and Learning, Sales Manager, Licensed Journeyman Plumber, Licensed Electrician,
HVAC/R Electrical Administrator, HVAC/R, Certified WA State C.E.U. Instructor

Bruce Sr is President of Day & Nite Plumbing & Heating, a 67-year-old family owned and operated plumbing and heating business in Lynnwood, Washington. Bruce can be contacted at: Email: Bruce@dayandnite.net

Day & Nite Plumbing & Heating Inc. 16614 13th Ave. W. Lynnwood, WA 98037 800-972-7000

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