In-line elec water heaters

[H Radec]

I am building a new house that, due to site constrictions, is rather long and narrow. No gas where we live in the country and electric heating is the standard in the Pacific NW. The master bath will be abt 40' from the main elec water heater if I put the main in the laundry room and abt 70' away if I put the main in the garage. Obviously, I will have to wait for hot water to reach the master and will waste a few gallons every time I draw it after the water in the insulated pipe has cooled down. I was thinking to put a smaller elec water heater in the master, say a 10 gallon one, plumbed in line that would give immediate hot water without waste.
For larger draws like a shower or filling a soaking tub I figure hot water from the main will reach the secondary after a few gallons and the secondary will mostly receive hot water and pass it through without needing to come on. Do you see any problems with this idea? I've read up on tankless/on demand heaters but am not entirely sold on them given the 'cold sandwich', maintenance and warranty issues with lime buildup, initial purchase and installation cost, etc, but I'm willing to entertain other solutions from your experienced opinions. Thanks in advance.

 

[Reach4]

I am not experienced, but your plan sounds good to me.

 

[Sponsor]

 

[Jadnashua]

That should work, but you might prefer to plumb in a hot water recirculation system. That way, any fixtures closer to the WH will also have nearly instant hot water. The controls on the recirculation system can be on-demand, but while not wasting water, you do have to wait for it, or you can use a time so it only runs when you expect to be up, or, some people just run it 24/7 (the pump itself is quite small and your main energy loss is from the uninsulated pipes - you can fix that!). You may not need a 10g WH to do what you want. Ideally, you'd have a hot water return line, but it will work by using the cold line at the hassle of the cold line becoming warm (they have a valve that closes once hot is at the end so that limits how much gets into the cold line).

The system I have uses an aquastat you can adjust to shut things off once you've got the temperature you want so that limits how much gets put into the cold line. Given how I have mine adjusted, flushing the toilet purges the warm water from the cold line so that gives you an idea of how far it pushed warm water.

 

[WorthFlorida]

Go with jadnashua suggestion of the recirculating system. With PEX it would be inexpensive to run a second pipe on the hot water side as compared to copper.

I did exactly what you want to do more than twenty years ago but I took it out in 1999. I had a long run from the water heater in the garage to the kitchen sink and dishwasher. Because of space and power limits I installed a 2 gallon point of use water heater under the sink. It worked OK but the cheap Made in Italy heater from Home Depot did not have an anode rod. In two years I decided to do a kitchen makeover and it is when I noticed the tank was leaking so I pulled it out.

Here is what happened as far as use with my set up. Because it was only a two gallon tank, running the water at first was fine, nice and hot but as the cool water in the 50 feet of pipe displaced all or most of the two gallons (3/4" pipe). I then had cold water until it used another two gallons before I had hot water from the main water heater.
With a ten gallon tank you'll may not have this problem since the approximately two gallons of cool water mixing with the 10 gallons of heated water you may not notice a drop in temp. But if a shower is in use, the water will start nice and hot, as it is used the temp will drop a little and you probably have to adjust the hot/cold mix. After the ten gallons or so are used up the heated water from the main heater will be at the shower, then the temp may rise causing another hot/cold mix adjustment. This may not happen or not be a problem but with a recirculating system, after a few seconds you'll have hot water at a steady temp. Since you are in the construction phase the third pipe is easily installed to for the return without the warm water in the cold water pipes.

Another solution is to install a second water heater (30 or 40 gallon) in the same location as you want to put the 10 gallon. Use this larger heater just for the far end of the home. It can be plumbed so a shut off valve on the hot water line from the main heater can be opened or closed if you ever decided to go with one heater. Yes, it will be two water heaters but each can be smaller but more likely will cost more in electric use.

 

[JerryR]

I installed a Redytemp recirculating pump at the furthest sink from the water heater, in the master bathroom. I have it set up as an on demand activation. I have a push button in the master bathroom and a few X10 switches, pool bathroom and pool area to activate the pump about 1 minute before we shower. It works very well for our needs. No wasted water down the drain.

Just before I use my electric razor I push the button. When I'm done shaving I go into the shower and the water is instantly hot. We love it.

https://terrylove.com/forums/index....er-heaters-at-point-of-use.65804/#post-494993

See link above

 

[Jadnashua]

I also have a RedyTemp unit. While others may end up less expensive, it is the only one I'm aware of that allows you to set the shutoff temp. In my case, it's underneath the vanity and the shower is closer to the WH. So by having warm water at the vanity, it's hot at the shower (and everywhere before it), so I get warm to wash my hands, but it's hot at the shower and that also minimizes the amount of hot/warm water back into the cold line.