Advice on choosing water heater.

[fold_em83]

I am replacing my water heater this weekend and I need some advice on which type to get. I currently have a 50 gallon electric tank heater. I am interested in replacing it with an on demand unit. I've done a little research on them and know that a gas on demand unit is a better way to go because it is more efficient. However, my house is all electric and I'm not really interested in plumbing gas lines at this point. What I want to know is even though an electric on demand heater is less efficient than a gas one, is it still more efficient than a tank heater? I've also read that some electric on demand heaters have problems keeping up with demand. I have a family of four (two adults, two children). My wife and I like to take very hot showers. Is there any unit that will be able to keep up with our requirements. Thanks for your help.

[LazyPup]

Whenever we enter into a discussion on the Pro’s and Con’s of “On Demand Tankless” water heaters it ultimately opens a real can of worms.

From the information presented in your post your primary interest in an “On demand tankless water heater” is based primarily on the claim of high efficiency. Let us examine the facts. It is true that the electric tankless water heaters are typically rated at 93% to 95% efficient, but on the other hand, a state of the art electric tank type water heater has an efficiency rating of 90% therefore I would agree that the tankless can save you 3 to 5% of the electrical utility cost that you would pay to operate a tank type heater, But; When we consider that a 50gal tank type electric water heater retails for about $300 as opposed to $699 for an electric tankless the question then becomes: at a 5% energy savings, how will it take to recover the additional $399?

Now let us consider the physical aspects of the energy requirement. You already have a 50gal electric water heater, which no doubt has a 220v 30 or 40amp supply circuit. By contrast, a whole house electric tankless unit will require 220v @ 90 to 120amps. In most cases the current electrical service entrance equipment on the house is not capable of supplying an additional 90+ amp load, therefore in order to install an electric tankless water heater it could require upgrading your entire electrical entrance equipment, the line down from the pole, the weather head, electric meter box and your service entrance panel. I am sure that Hayzee or one of the other electricians in the forum could give you more details on this but I feel it would be safe to say that this could easily increase the cost of the retrofit by $1k or more.

You also stated in your post that both you and your wife enjoy very hot showers. The proponents of tankless water heaters argue that a tankless will provide an endless supply of hot water, but the question then becomes, what is hot? A tankless water heater is designed to raise the temperature of the incoming water by 70degF. In mid summer when the incoming cold water is in the 50 to 60degF range it can produce an unlimited supply at 120-130DegF at the full rated flow, however, the plumbing codes require the water supply line to be buried 6” below the average frost level. Here in W.Pa where I live our frost level is 36” and our water lines are typically about 40 to 48” deep. As a result in mid winter our incoming cold-water temps are 36 to 40degF. This means that at peak performance in mid winter a tankless will only produce hot water in the 106 to 110degF range. Also, a tankless will only produce its full rated flow when the incoming water is in the 50-60degF range. As the cold-water temperature drops a tankless automatically throttles back the flow rate to allow time to heat the water thus, where the tankless may be able to produce 6gpm in mid summer it may drop to 3gpm or less in mid winter.

[pbc]

good stuff lazypup.
answered a LOT of questions I had about the on demand heaters

[LazyPup]

The original question was relating to replacing an electric tank type water heater with an “on demand tankless water heater” and I pointed out that in many cases it would require upgrading the house electrical service entrance equipment. It must be mentioned that the same is true of retrofitting an existing structure with a gas type tankless. Although a tankless water heater does not consume energy during periods of non- use, it must be understood that the energy requirements when firing are extremely high. Typically a gas tankless requires the same amount of natural gas, as would a gas furnace. In many instances in order to provide the necessary gas we have to increase the size of the entire gas line from the municipal main to the structure. From this you can easily see that retrofitting an existing structure with a tankless water heater can pose a number of rather expensive problems.

I also pointed out that while a tankless may be rated high enough to provide the total gallon per minute demand of your house, that rating is the maximum rating when the incoming water is at the natural geothermal ground temperature of 50-55degF, however in the colder northern climates the rate of flow will diminish as the incoming water temperature drops.

In all fairness to the tankless technology it must be mentioned that if you are building a new house you will be initially installing the electrical or gas service, and in this instance increasing the size of the electrical equipment or gas line would only present a small increase to overall cost of installing the service.

If you are building a new home in the sunbelt where the incoming water will always be at the natural geothermal temperature of 50-55 or higher from warmer surface soil temperatures a tankless water heater might offer a good alternative.

One of the downsides of a tankless system is that most of them cannot support the minimal rate of flow required to maintain a circulating hot water loop to provide instant on hot water. This problem can be easily overcome by installing a small 2 or 3gallon electric water heater immediately downstream of the tankless, we can then connect the return line of the loop back to the small tank. In this manner the small tank can provide the necessary hot water to keep the loop functioning.

[pushkins]

I know this will stir up a hornets nest !

Ya know I gotta say one thing, why is it that here in the US the info on the use of tank less h2o systems seems to be always on a negative aspect ?
All across Europe, Asia, Australia, New Zealand and Africa tank less systems are and have been in use for decades. I come from one and have lived in three of these areas for extended periods of time and never has it been a problem including in Russia, where I can assure you the temps. get cold.
I keep hearing that the on demand capabilities of tank less are poor and won't supply enough water or hot enough water, well it seems to do all of the above for more than half the planets population.

Granted American homes are more sprawling than most European homes, so getting hot water from one end of the house to the other is always going to be a problem, the solution in large homes in Europe is to have one tank less for the bathrooms and another for the kitchen/utilities.
Colder climates like Russia and northern Europe tend to have indoor tank less heaters (also a space issue) and more temperate climates like Australia and Africa almost all are externally mounted units.

In the days of water conservation 2.5 gpm shower heads are now known as rain heads and 1.6gpm are water savers, so the min. gpm of a tank less is almost ( I did say almost ) irrelevant.
In most cases in most homes here in the US if two people are taking a shower at the same time with a standard h2o system (tank), someone gets to scream about the lack of hot water. (just try flushing a toilet while your wifes in the shower....lol) I know this might seem like a generic statement, but lets face it, just how many houses are built and plumbed with two or three showers running at the same time in mind ?...

Hot Water = 130 to 135°F at this temp. the water is too hot to touch without injury, no one I know can tolerate a shower this hot, mostly the temps are in the 110 115 F range and even here this range is a HOT shower.

Friends in central Ohio put a tank less system in, in fall last year, Ohio was unseasonably cold and they never had a problem.
Yes I do agree with Lazypup on the electrical requirements of a tank less system, in some cases you should beef up the electrical needs but if you have a furnace for heating then the gas is there , it just needs to be run to the new tank less heater.

[fold_em83]

Thank you, LazyPup. You answered a lot of my questions. I think I will just use another tank heater. I would like to make sure I'm doing the right thing though. The reason I am replacing the heater in the first place is not because it leaks or isn't heating the water properly, it just seems like the hot water doesn't last very long. Both elements are new (3 months old) and both thermostats are working properly. They are both also adjusted to one setting lower than the maximum. But when you take a shower, the water is getting colder within five minutes. You can adjust it two or three times and get hotter water again but after that, its just cold. Am I doing the right thing with replacing the heater? I'm a little concerned that this is a normal condition and the only thing I'll accomplish by replacing the heater is wasting about $400. Thanks again for your help.

[HayZee518]

you have to understand that an electric hot water heater isn't really Hot on Demand. it takes time for the elements to heat up. in an oil fired hot water tank you have almost instant heat when it fires up but mind you the rest of the tank needs to heat up too. I had an oil fired hot water system in my first house and you couldn't kill it with the sink faucet wide open, the shower going full blast etc. restaurants use the hot on demand systems for their dishwashers but this is a big unit! some of them use three phase power to fire it up. Chromalox makes several on demand heaters but you are talking 4-6 kilowatt elements that operate "at once" to provide the heat you need at the expense of the "owner" of the restaurant.

[LazyPup]

Based upon the symptoms you describe I would be very hard pressed to recommend replacing the whole water heater.

You state that your hot water is running out after 5 minutes in the shower. Allowing that the old style shower heads had a flow rate of 5gpm while the new water savers have a flow rate of 2.5gpm at the end of five minutes depending on what type of shower heads you have, you have consumed somewhere around 12.5 to 25gal of water.

Typically a 50gallon electric water heater has a “First Hour” rating of 50 to 60gallons, which means that if the tank if full of hot water when the flow begins, it should be capable of delivering 50 to 60gal in the first hour of the demand. Obviously your water heater is not delivering the expected first hour flow rate so we must now consider what could cause the problem.

Ask yourself a simple question. If you have a hot cup of coffee sitting on your desk while your reading this, and if that coffee gets cold, will you throw the cup away or will you simply pour out the cold coffee and get another cup? Just like in our illustration with the coffee cup, if the tank is not leaking there really is no justification for replacing the whole water heater.

An electric water heater is simply an insulated steel pressure vessel with, a Temperature & Pressure relief valve, a drain valve, a dip tube, two thermostats and two heating elements,

We can instantly rule out the drain valve and the T&P valve as the cause of your problem.

Based upon the symptoms you describe and understanding that this is a sight unseen diagnostic, my best guess is that you either have a defective dip tube or the upper thermostat or upper heating element is not working.

You previously stated that the elements have been changed, however there is the remote possibility that the new element has failed. Given that accessing the thermostats and heating elements is fairly simple it would be prudent to thoroughly check both thermostats and heating elements before taking any further action.

The quickest and best method of checking the heating system is to use a “snap on amp meter”. You simply snap the jaws of the amp meter over one wire on the lower heating element then open a hot water faucet. Within a few moments you should see an amp reading indicating both the lower thermostat and heating element are working. Continue running the hot water and in a few minutes the lower element will turn off, indicating a zero amp draw. When you get the zero amp draw, remove the amp meter from the lower element and attach it to the upper element. If it shows an amp draw at the upper element both the upper thermostat and upper heating element are working.

Let us consider the dip tube. The dip tube is a plastic tube inside the water heater that extends downward from the cold-water inlet to a point near the bottom of the tank. The purpose of that tube is to carry the incoming cold water to the bottom of the tank while the hot water is discharging from the top of the tank. If the dip tube were broken the coldwater would discharge into the tank near the top. This results in diluting the stored hot water near the top of the tank and the end result is a rapid drop in the temperature of the water leaving the tank.

Before you begin the procedure to replace the dip tube you should get a new dip tube for your water heater. To insure you get the correct dip tube you will need to know the Make and model of your water heater then go to a plumbing supply house or a local neighborhood hardware store such as an Ace hardware or True Value hardware. (Most big box supply centers don’t want to be bothered with trivial items like dip tubes) They may not have your particular dip tube in stock but most will be glad to order you one. Expect to pay about $10 for a dip tube.

To replace a dip tube you pull the electrical service disconnect and turn the cold water supply valve off, then you will need to drain the tank. Once the tank is drained you disconnect the cold-water supply line and if your tank has dielectric nipples, you will need to remove the nipple from the cold-water inlet port. The dip tube is simply a plastic tube that drops down the cold-water inlet port and is held in place by a small flange on the top of the tube.

You pull the old tube up and out, then drop the new tube in place, reconnect the pipes and fill the tank.

NOTE: if the old dip tube should happen to break off inside the tank; that is not a problem.

Now let us consider the economics of completely rebuilding an electric water heater as opposed to replacing it.

You stated that you already have a price of $400 for a new water heater +2hours labor as a DIY project.

Now let us consider a worst-case scenario where you need to buy all the parts for a total rebuild:

Upper Thermostat…………………………………..$13.00
Upper heating element (220v 4500watts)…………..$10.00
Lower Thermostat…………………………………..$12.00
Lower heating element (220v 4500watt)………...…$10.00
Temperature & Pressure Relief valve………………$10.00
Brass boiler drain cock……………………………...$ 8.00
Dip Tube…………………………………………….$10.00
TOTAL REBUILD PARTS COST…………. $73.00

DIY Labor estimate.. 2-4 hours

Now consider this. Sears sells a Craftsman snap on amp meter for about $60. If you opted for a professional grade such as the Sperry SPR 300 that I use, you could get it for about $150.

Even if you had to buy the test instrument you could still end up with essentially a new water heater for 1/4 to 1/2 the price of replacing your existing unit.

[fold_em83]

I'll keep that in mind. Thank you. Part of my reasoning for replacing the heater is because I recently bought this house and I have no idea how old the current heater is. I can't find anything with a date on it anywhere. I had read about the possibility of the dip tube being broken but I did not realize that they were serviceable. Also, please let me know where you buy your heating elements from. I think i paid nearly $25 each for mine at my local hardware store. All of the other ones were in the $13 range except for the ones that matched what I already had.