Water heater for addition

[JackOfDiamonds]

I'm planning a 500sqft addition to my 1800 sqft house.

The current 40gal water heater is barely enough for the house as it is. And the addition is as far away from the existing heater as possible.

There's two things I hate, running out of hot water and having to wait a long time for hot water. With the new water saving fixtures it seems to take forever for water to turn hot.

I could upgrade my current tank to a 80gal bigger one. But I would still have to wait a long time for hot water in the addition.

I could put a "booster" tank in the addition. One of the lowboy jobs. But I'm not sure if I should plumb that in series with the primary, or just dedicate it to the fixtures in the addition. I'll have a big tub, so a small tank might not be enough if it's plumbed dedicated.

I could put a tankless in the addition. I'd have to run gas, they are hella expensive, I never liked how long it takes for the water to start coming out hot, and it doesn't do anything about my marginal main tank.

I could just upgrade my main tank to a big tankless for the whole house with addition. Doesn't solve my problem of having to wait a long time for hot water, but it would fix the capacity problem.

I could install a tankless as my main water heater, then put a little electric booster in series in the addition, so I get instant hot water AND infinite capacity. Os that possible?

What would you do?

 

[Jeff C]

Is the current one electric or gas? Sounds like you have gas available at least. IMO gas is the only way to go if available for a water heater whether you do a tank or tankless.

I’ve always been fond of a tankless but never really had any complaints when I had a natural gas tank water heater. Now I’m stuck with electric and not real crazy about it.

 

[nadogail]

I have a 120 volt 3 gallon water heater with a pretty fast recovery. I have it connected to the sink in my workshop. I am sure I could get a "Navy Shower" out of it. if you feed your little heater from the output of your big water heater you might have endless hot water. The water heater was less than $100, five years ago, if I recall correctly. Home Depot sold me mine.

 

[CombatNinja]

What is the 500 sq ft addition? As in, what kind of space?

 

[JackOfDiamonds]

My current tankful heater is gas. So I have gas in my house, but running gas to the addition would add cost. It's pretty far.

Tankless heaters require a lot of gas. More than a furnace. So I might even need to upgrade my gas service, or upsize my lines to do tankless.

 

[Jeff C]

If you run two water heaters in series does that mean you have a COLD water heater AND a HOT water heater?

 

[fitter30]

Heaters in series have draw backs u don't get the total of the two of hot water, first water heater get most of the minerals out of the water. Parallel piped reverse return get even flow between the two even if there mismatched. A return line from further fixtures with a small pump will give u almost instant hw. Garden tub or muilti head shower need a tankless. Need max gpm flow, coldest entering cold water and temp used to properly size the heater. Heres a water calculator for mixed temps just change to gpm and f°. Any temp above 120° need a mixing valve on hot water.

Water Mixing Calculator | Spirax Sarco

This calculator will help to consider the mixed temperature of two water streams, its flowrate, percentage flow and actual flow of each stream.

www.spiraxsarco.com

 

[Walkers]

Upgrade your current WH, run a return line to the tank for a pump. Put a switch wire in with the pipe. Put a switch in the bathroom to run the recirc pump until the hot water gets there. There are also the recirc pumps that fit under the bathroom sink. They just move the cold water from the hot side to the cold side until the hot side is hot.

 

[Glemon]

I had a similar problem with the addition (master bath off the bedroom) in my fifties ranch. I had a out a 70' run of 3/4 pipe, took about a minute to heat up in my low flow sinks.

I put a 7 gallon 110 volt electric heater in series in the crawl space under the bathroom. It works great, enough volume to "buffer" the cold water hitting the aux. heater until the hot from the main heater kicks in, so I get quick hot and no discernable rise or fall in temp (adjusted the little heater to match the big one). Full discussion and link to model bought, as well as plenty of other suggestions) here

https://www.garagejournal.com/forum/threads/hot-water-heater-in-series.491628/

 

[Renegade1LI]

If you have the room consider a hybrid electric, very efficient, I'm installing one next week. No gas or venting & 1300$ in rebates.

Rheem Performance Platinum 50 Gal. 10-Year Hybrid High Efficiency Smart Tank Electric Water Heater XE50T10H45U0 - The Home Depot

The Rheem ProTerra Electric hybrid is the smartest, most efficient water heater on the market. Heat pump technology makes it 3X MORE EFFICIENT than a new conventional electric model (of the same capacity).

www.homedepot.com

 

[klassenl]

Don't get a new tank. That's a waste of money. Run a hot water circulation line with a small pump. And then get the kids to take shorter showers.

 

[Glemon]

I considered all options, in my case a recirculation line didn't make sense because I would have had to tear out an old tile ceiling to insulate the long run.

 

[u3b3rg33k]

small diameter pex should get hot water there pretty quickly. just take it off right after the heater, not at the end of the existing trunk.

 

[Mzungu]

Several good options as stated
- 1/2" pex straight from the hot water manifold. (good)
- recirculation pump (better)

 

[duneslider]

I have two water heaters in series and with 5 kids we have never had a situation where we ran out of hot water. I have read all the arguments of series and parallel and they all the seem to have plus and minus' from what I read, my plumber said his recommendation was in series and thus far it has worked great.

I have an on demand recirculation pump on mine for one bathroom that is furthest away, we only turn it on when someone is planning to take a shower or bath.