One, Two, Or Many Hot Water Heaters?
 

Hi Everyone,

My family and I are in the process of renovating a house. As part of that process, I wanted to go full point of use. At minimum, one for each bathroom, one for the kitchen, and one for the clothes washer.

However, my family is telling me that is a waste given the proximity of the bathrooms. The three on the second floor are more or less a "T" shape, and according to them it is virtually impossible that more then handwashing we be done at the same time in all of them. The downstairs bath is a half bath, and the kitchen is immediately behind it-but the sink and the washer/dryer hookups are on the opposite side of the kitchen from that wall.

Their suggestion is to setup two: one to feed the upstairs and one to feed the downstairs.

I'm wondering if, at that point with the potential sizing, if it wouldn't be better to just go ahead and get a single tankless unit large enough for the average demand of, say, clothes washer plus all the sinks plus 1 or two showers and and recirculating pumps.

What would you do?

I tried that, just go with one hot water heater.
The idea of a point system is say you have a part of the house that's far away and you can barely get cold water to it let alone hot water, then do a point system.

When my parent's built their home (1750sq ft} they wanted instant hot water in the kitchen.


The solution was a single tank heater with an Instahot tankless at the kitchen sink.

I had a similar problem. Then I thought it through and realized that the wash machine and showers were "big" users where flushing the cold water out of the line was a small percentage of the total water. The "little" user was the kitchen sink where we draw small amounts of hot water many times per day.

We went with one 40 gallon hot water heater that feeds everything. The kitchen sink has a 2 gallon water heater under the sink. The 2 gallon heater means that we waste about 1/2 pint of water before the hot water comes through. After about 1/2 gallon of hot water, the hot water from the water heater gets there. It works very well.

I had to replace all the plumbing in my first house. I ran 3/8" copper directly from the water heater to the kitchen sink, and to the bathroom faucet. And larger lines to the shower and to the wash machine. It took about 1 pint of water before the faucets got hot, and pressure drop was minimal.

Remember that tankless heaters have a minimum flow rate, and the temperature is a function of both flow rate and incoming water temperature.

Small pipes is a good idea for quick heat.

I've got one 10 gallon heater. I didn't know they come in 2 gallon size.

Our kitchen takes ages for hot water (maybe 2 minutes). Low flow aerators contribute to the delay. We've got a 1 gal hot water on demand unit for making tea and providing 180 degree water instantly for cleaning purposes.

Best solution is probably something that circulates the water to keep pipes hot, and a single tank.

Insulating the pipes to retain heat would also be desirable, to increase overall efficiency of the system.