Update: changed out the cartridge in the shower valve... it was full of gunk... shower now works as advertised. This probably should have been done 25 years ago when I moved into the house.


I am thinking adding an electric tankless water heater (gas isn't available in my area) between the existing 50 gallon water heater and the shower to keep an unlimited supply of hot water for a long shower, or for days when three people have to shower one right after another (wife, me, and son) so that I don't end up with a cold shower.

Does this seem like it would work? I know the electric models may not be as efficient as the gas models.

Would installing this between the water heater and shower be beneficial or just a waste of time and money?

This message has been edited. Last edited by: lizardman_u,

The only thing I’ve heard about them is that they use even more juice than the traditional tank kind so you may not be saving any money if that was your goal plus the investment cost is way higher than the traditional ones.

Based on what you are saying, the problem lies with your main water heater. I have a 50 gallon water heater and never run out of hot water, and I have three little kids and a wife and everyone is getting baths and showers all the time.

My son-in-law's brother is a plumber and installed our latest water heater a couple years ago.
I was considering electric tankless as we don't have gas available, either.
He told me the electric versions are all junk and the only way to go tankless is with gas.

My plan was to use the tankless as a booster for the main water heater.

Main water heater is only a couple years old. The problem could lie in the shower valve letting more cold than hot water flow. Shower valve is most likely as old as the house.

Thank you both for the replies.

just get a bigger tank, or more easily if you don't want to ditch your current tank two inline. The tankless stuff on electricity really don't work that well.

As with anything, if its sized and installed properly, its gonna work.

Even the ole mighty ELECTRIC on demand water heater!

It's funny how the gas tankless people always defend their 200K tankless, saying it only uses that much gas when it operates.
But, when it comes to electric on-demand "they use even more juice than the traditional tank", well no shit. But how's that any different then with the gas unit?

Take a look at Siesco or Stiebel.
And as with the gas unit requiring a larger gas line, you're gonna need a 200A panel to feed the electric unit.

Because converting gas to heat to electricity to heat is probably not as efficient as converting gas to heat. I could be wrong.

I installed one for point of use at a bar sink. First issue is that the 110 volt units aren't efficient at the flow rates to get working hot water. Thye are a joke. I had to choke it down to a trickle to get handwash warm. To get hot water means running 240, which is the type we had in our auto parts stores, for hand washing - not showers. Those delivered more than adequate amounts of hot water but cost as much or more than a 25 gallon tank unit.

Flow rate is critical as I mentioned, too fast thru the unit and no hot water. It needs dwell time and a heater big enough to do it.

I've considered a small 3-5 gallon water tank - about twice the physical size as the heater - for the kitchen sink due to the long run. The pump units are also available, which recycle the cold back against the line and the hot comes in pretty quick with those and no water down the drain. For showers, tho, 50 should be enough.

Growing up we had a 30 gal with 6 in the house, yup, parents had priority and if you were last, then you plotted against your sisters excessive use, up to and including flushing two toilets or shutting off the hot valve on the heater. Now the safety shower valves prevent that. Oh well. We run a 50, which was good for 6 here at one time and a bit overkill for 3 now. It winds up heating more hot water than we need but it's expensive to downsize unless you need to replace it.

One efficiency tip for a water heater is to insulate it better - mine is in a basement/garage which hits 45F all winter. It needs it's own insulated closet, with a water pan and drain system.

My water heater is a 50 gallon electric unit installed in the center of the house. However, I think the water lines run under the house and so even though insulation covers them (the bottom of the house is insulated) they come up to the shower valve which tees to a frost free faucet valve for a hose bib outside. This arrangement I think lets water cool as to replace the frost free bib one had to cut a hole between the bathroom and bedroom walls.. no insulation in that wall as it is an interior wall even though this part is less than two feet from the exterior wall.

quote:

Originally posted by trapper189:
Because converting gas to heat to electricity to heat is probably not as efficient as converting gas to heat. I could be wrong.

Wasn't meant as a question... it was more of a comment, even though it ended with a question mark.

Electric is 100% efficient
Gas is up to 98% efficiency

Btu is Btu, no matter gas or electric.
Cost per Btu is where the savings is, using the cheaper fuel source. Natural gas is normally cheaper for most areas.

Then you have the same argument for both (gas or electric), they use a large amount of fuel *only* when they are in operation. So there's no standby loss with either. Both tankless units will save money in operation over respective tanked units.
The problem comes with expensive installation, maintenance and repair costs. Offsetting any savings with operation.

Of coarse, theres always the advantage of having endless hot water.

No experience with electric tankless in the US, though it worked great in multiple flats in and around London years ago. Absolutely love our (propane powered) Rinnai. Probably not any cheaper, and with one of the teenagers off at college may be less necessary, but damn endless hot water is a beautiful thing!

For the cost, I am NOT impressed with the one I installed 2 months ago.

I wonder how the electric tankless in line with the present heater would decide to come online, when fed heated water. IF the water reaching it was 100 F, down from 110 F from the first heater, would it come on? At what point would it decide it was time to fire up the resistance heaters? How would the high amperage lines be run to the new heater? Are there spaces for the breakers in the current box? (In mine, there was space for another 220 v outlet for a 30 amp device).

We’ve had two water heater threads in the last few days. Both were about electric heaters with insufficient performance. In this case, the complaint was about three person hot water capacity, and for many years my 50 gallon electric would handle four people. This suggests the existing heater would work. In the other thread, there were good questions about the state of the water heater, that would help diagnose the capacity issue. Is the drip leg still in good shape? Are both elements actually working? It sounds like here the same questions would be good to run down before doing anything major.

Some numbers on using the shower: Average of ten minutes with a 1.8 GPM head, 18 to 25 gallons of hot water each. Sounds a bit much, and then goes to recovery rate for the normal tank using both heaters. Can it heat up the new incoming water in less than 20 minutes?

My bar sink was rated at .6 GPM. That meant turning off the valve under the sink down to about a third or less to slow the rate. You can test using a quart jug, it should fill in 30 seconds - no sooner - to get .6. A standard set up would be 1.8 which is almost 2 gallons a minute.

That's why the GPM rating of a tankless is important - and it takes more money to get the rating up by a factor of 3 to achieve what I expected. A shower is going to need one rated to produce continuously at 1.8GPM - if that is the shower head rating - for ten to fifteen minutes and not fall behind. Getting one too small is disappointing, but for me it was just a small sink rarely used.

Friend has five people in his house and they have the electric tankless heaters. They have three of them. All of them need a 200a feed. You can get hot water anywhere in the house even with three teenagers running a shower, but I can’t imagine their electric bill.

I looked at one that would handle a single shower, it needed a 60 amp 240 volt Circuit to power it.

My issue may be a partially plugged hot water line as we have hard water, or it could be a partially plugged shower valve as it seems we get more cold water in the shower than hot. If I want the shower to last enough time I have to turn the volume of water down at the tap.

House is 40+ years old being built in 1978, and I am sure it is the original shower control valve.

Maybe there is a way to clean it up without tearing out the tub surround.

quote:

Originally posted by lizardman_u:
My issue may be a partially plugged hot water line as we have hard water, or it could be a partially plugged shower valve as it seems we get more cold water in the shower than hot. If I want the shower to last enough time I have to turn the volume of water down at the tap.

House is 40+ years old being built in 1978, and I am sure it is the original shower control valve.

Maybe there is a way to clean it up without tearing out the tub surround.

You know you don’t have to tear out the whole thing, right?

We had 70 year old separate hot and cold knobs in our showers and I had them retrofitted with modern mixing valves and they cut into the tile then covered it with a plate like in these pictures I found online. We had two showers done and I think the plumber charged $600 each to do them:

quote:

Originally posted by lizardman_u:
My plan was to use the tankless as a booster for the main water heater.

Main water heater is only a couple years old. The problem could lie in the shower valve letting more cold than hot water flow. Shower valve is most likely as old as the house.

Thank you both for the replies.

As an aside, I just had this problem, but it was because I had hard-water deposits built up on the filter screens in the hot-water supply tube.

Found that out while installing the (very expensive) cartridge for my panel shower. Well, now I have a back-up.

Have had tankless electric for 20 years and really like them. Would not do without!