In Deep Hot Water

In Deep Hot Water was Originally Posted on March 25, 2007 by lavarock

(or more about hot water heaters than you wanted to know)

My house is fairly small, with 2 full baths and half bath added later downstairs. There is a washing machine but no dishwasher. Thus, the hot water heater is only a 38-gallon unit, which is probably half the size the average house would have.

I knew the hot water heater was in trouble because the side was starting to rust out. Of course, the closer you are to the water, the faster the rust, but I am miles away.

To heat water there is usually an incoming water feed, a large tank where the water is heated and an outlet pipe feeding the house The water may be heated by natural gas, propane, electric, or in older homes, wood, oil or coal. Most common in this country is electric or gas. Here in Hawaii I think the most common is electric and perhaps solar where the sun heats the water or at least contributes to the heating.

The type of heat source depends upon a few factors, which fuel is available and at what cost, and also perhaps the incoming water temperature. On the mainland US, most water is supplied from underground pipes. They keep them well underground to avoid freezing during winter and to keep people from easily damaging them when digging. This water may enter the system at perhaps 50 degrees or so. If you really care you can look it up, but I seem to remember caves and underground water is perhaps 50-some degrees. Here on the Big Island (because we lack deep soil and many live in farm areas) the water may be all above ground. It is not uncommon in South Kona to see white PVC or black plastic pipes feeding farms and houses; these lines all above ground. Besides being easier to repair, the water is warmer when entering hot water heaters. Ever notice when you leave water in a garden hose and turn it on, the water may actually be too hot to touch for a few seconds? I guess I could consider putting a big copper pipe up on the roof and let the sun do more heating of the water.

Inside an electric tank are two thermostatic-controlled heating elements, not unlike the ones on your stove. The water fills up the tank and then sits. The thermostat detects cold water and turns on the electric to the coils, which begin heating the water. When it reaches the desired temperature, the thermostat shuts off the current to the coils. Even though the water is in an insulated tank, it slowly begins to cool off and soon the thermostat starts the cycle all over again, keeping the water at the right temperature should you need it. Other fueled systems operate on a similar principle.

As you know, water arriving at your house is not perfectly clean. It has minerals and particulates in it that can cause problems. In a system with a tank, these particulates settle in the tank and unless the tank flushes itself, the owner should periodically (following the proper procedure) remove this stuff from the tank. I say properly because if you drain the water out of the tank while the heating source is still active, you risk damaging the system. It will only take a few minutes to destroy electric heating elements with no water around them.

Sediment (tiny pieces of sand or rock or stuff from pipe fittings) accumulates in the tank and should be flushed out. Also, the water itself may be a problem for a hot water system. Tanks may include a sacrificial rod that will react with water to ensure the tank lasts longer.

When replacing hot water heaters, put a pan underneath and drain it, in case the bottom rusts out. Mine did not have such a pan and the unit just burst open. Luckily I caught it soon afterwards before major damage was done to the floor.

I’m looking to replace my water heater and am considering a tankless, on demand) system. In this type of system, the cold water enters a small unit on the wall and when heated, exits on the other side. Think of it as a very small radiator, fueled by propane, electric or natural gas. This unit may be only a couple feet wide and tall and has essentially no moving parts. Rather than store perhaps 70 gallons of heated water, they just heat the water continuously as it flows through and the thermostat shuts off the unit completely when no water is being used. Unlike systems with tanks, there is no fuel used until you turn on the faucet, then the water is instantly heated and delivered to the faucet.

If you think about how the tanked system is constructed, as the hot water in the tank is used, cold water, perhaps at that 50-some degrees enters the tank and begins mixing with your precious hot water, diluting the temperature and dropping the water temp down the minute you start to use it! With the tankless system there is no place to mix the water and thus will send continuous hot water with no fading like you get with the big tanks.

I understand that since the tankless systems are not cycling on and off or storing water, they are more efficient, however, they do require more fuel because they are bringing the water up to the delivery temperature quicker, however, when you are done with the water, they shut off, rather than enter a standby mode. No longer would you need to shut the thing off when you go on vacation.

There may be a few drawbacks though. Because the water does not start getting cold, you have to be careful that you do not stand under it for hours! I am sure that is a common thing people do when they stay at a hotel with what appears to be unlimited hot water – stand under the flow for the longest time. Also, without a tank to trap sediment, there may be a need to unscrew those faucet aerators and clean them more often. Sediment also accumulates right there if you use them.

Another issue (like with the electric units) is that unless you use smaller on-demand units close to where the water needs are, you may have to beef up the electric for the main unit as it may require double the electricity the current tank uses. As an aside, they make small 110 volt units that you can put under a sink to supply an out of the way location or perhaps mobile home bathroom.

Here in Hawaii, my electric bill is high. I changed over to fluorescent lights, try not to use the oven much, use no heat or air-conditioning and am constantly thinking about economy. Still, my electric bill is $150 a month! Although that sounds high, I have no other fuel bills like gas. Back in Georgia I could spend $150 just on heat for a month and one month spent over $400 just to heat the house. Granted it was a big house and we had a blizzard…

These tankless systems appear to cost perhaps twice the costs of a tank, so I may spend $400 or $600 for a unit. However, at $400, I think that my savings in standby electric costs here would pay off the system after just 6 to 9 months! Granted, mainlanders might take a year or more, but I think I would save at least $50 a month or more here!

So I think you can see why I am considering a tankless system. I believe there is an energy credit that will offset some of the cost of the unit too.

At this point, I’ll be happy just to get the water mopped up in the utility room and get running hot water back.

If you get interested in this topic, you might consider investigating these tankless systems. They may not be for everyone, but then again, they may work for you.