Hello.

We are managing a 4 unit condo association and have started to run into hot water problems. We have a 120 gallon electric water heater for the entire building (I don't have any other specs right now but will gladly get them if necessary). There are 9 people living in the building. The only time there is really a lack of hot water is between 6:30-9:00am. There are 4 dishwashers and one washer/dryer combo (which is supposed to be energy efficient and partially heat the water it uses). Another owner had a plumber look at the tank and I believe made some modifications (changed elements and increased the temperature of the water)

Is a 120 gallon tank too small for a building this size? Any recommendations on larger tanks or ones that heat up quicker? I don't really know what brands to look for.

Thanks

Yes a 120 gallon water heater does appear to be a little small for that size.
How old is the heater? Perhaps one of the elements failed. Very common occurance. Also how hard is the water. One very common issue with electrical heaters is the heating element builds up with the hard water deposits. Makeing it harder for the heater to properly reheat the water.
Still another problem could be the amount of water being used. Did the owners change the low water spray heads? If so this would allow additional flow out of the shower heads thus use more hot water then the unit can supply.

As far as replacement. Its not the make your looking for its the recovery time. So when comparing heaters that is what you want. Once that has the fastest recovery time as compared to the rest you look at.

If all else fails you can always do one of the following things.
Install individual on demand units for each homowner.
Install a second heater and put them in parallel pipe wise so you have more capacity.
Not allow dishwashers. Many condos do not allow for these devices.

Thanks for the reply. The heater is only about a year or two old. Elements were all changed and temp was raised as high as is reasonable. I don't really know how hard the water is, but I would assume because the element was changed, it's not a problem. Do those deposits build up that quickly? (element was changed less than a year ago)

I'm leaning towards two heaters in parallel. The price of a larger rapid recovery heater I was quoted (not from a very reliable plumber) was $9000 with installation. This seems a bit unreasonable. If we were to get a second tank that was smaller in size, would that be put before the larger 120 gallon tank? Is there an optimal way to order them?

Thanks again.