We were told that because we do not have sufficient hot water for more than one shower, calcium in the heater is the problem and we need a new one. Do we?

Mineral build up, such as calcium, occurs when the water heater isn't flushed out on a regular maintenance schedule. Chances, are unless the boiler's leaking, it can be revived
Before we much farther I need some information. Gas or electric? How old? Did the shortage of hot water start suddenly or come on gradually? And lastly, Hoe did the person even know the tank had calcium built up in it? Or was it simply a guess on someone's part? Back to you, Tom

Sounds like you got that advice from a water heater salesman. Answer Tom's questions. If you supported more than one shower before we should be able to get you back to that again.

Mineral build up, such as calcium, occurs when the water heater isn't flushed out on a regular maintenance schedule. Chances, are unless the boiler's leaking, it can be revived
Before we much farther I need some information. Gas or electric? How old? Did the shortage of hot water start suddenly or come on gradually? And lastly, Hoe did the person even know the tank had calcium built up in it? Or was it simply a guess on someones part? Back to you, Tom

The heater is gas. Installed in 1992 and the salesman just said that this was the problem.

"and the salesman just said " so I guessed right. I replace water heaters when they leak or the functionality fails, I flush them when debris is building up in th tank. Do you need help with how to flush?

Hi Ryandrew,
You are lucky that your 18 years water heater is still working, like both experts says if it is working you need to flush your water heater, Tom suggests every month but I do mine every 3 months, if you need help with come back and one of us will walk you through, good luck.

John

Let me take you through it now.

For long life and fewer troubles you should keep your heater clear of mineral build-up by FLUSHING NOT DRAINING on a regular schedule. Attach a hose to the boiler drain at the bottom of the tank. With the pressure on, open the boiler drain and let it run until the water runs clear. You will see a spurt of red,(rust) followed by white or yellow grains,(lime or calcium carbonate). This shouldn't take more then a few minutes. Do this monthly to keep it clear. Now flush out your hot water lines on ALL fixtures that are affected . Now pull each aerator and clean the screens. Be sure you put them back together the same way you took them out. Don't forget to flush it out every month. Your heater will thank you for it. And just for the record it doesn't make any difference about the age as long as the boiler's intact. I have a Caplan one counter top water heater that came with the house when we bought it. That was over 50 years ago and it still works. Flush the mineral build out. It's been building up for 18 years And insulating the flame from the boiler.
H ope this helps and thank you for rating my answer, Tom