We need more hot water in my house! I resently added a new bathroom
with large (5 head) shower and a 125 gal. jetted tub. I currently have
a 50 gal. natural gas water heater that is about 2 years old in the
garage. If I fill up the tub, then I don't have enough hot water to
shower afterwards. Even one long shower will get cool towards the end.
We are having a baby and my mother-in-law will be staying with us for
a couple of months so our hot water useage will be going up! I have
found and priced larger (100 gal.) water heaters. They are quite
expensive! I considered installing a point-of-use water heater to fill
the tub. Good ones of these are also quite expensive and the
installation (including a gas line) in the attic could be expensive. I
am leaning toward buying a 2nd 50 gal. water heater and installing it
next to the existing one in the garage(there is room). My questions
are: What is the best way to connect them (parallel or series)? Is
there any special requirements for these water heaters? Is there
anything else that I should know? Is this a common practice? Thank
you!

I would first try setting the temperature higher on the existing
heater for more thermal storage. Just be careful about mixing enough
cold at sinks and shower.

Higher temp makes sense. You'd use less hot to achieve the same temp.

I don't know how you would hook it up, but I would rig the second tank
so that the system would drain one, then switch ot the other and fill
the empty one. Everybody's experienced having warm water because the
tank started filling with cold when it was half full.

If you are having a baby HOTTER WATER IS NOT WISE (says this Father of
four). It may not seem relevant now, but in about 1 1/2 to 2 years,
your little one will begin to experiment with the faucets, in both the
sink and in the tub. It only takes a second to get scalded. Besides,
everyone else is already conditioned to turn that hot water all the
way on to get better results. An adult is just as likley to get burned
washing dishes or taking a bath as is a child. The amount of heat that
would have to increase in order to have a significant impact on your
hot to cold ratio would be far hotter than what is considered safe,
expecially with toddlers in the house. You'll probably find yourself
turning it back down for safety reasons eventually (not to mention the
fact that the higher the heat, the shorter life your heater will
have). You may even find yourself buying another hot water heater to
replace the one your burned to a crisp.

If it were me, the first thing I'd do woould be to call a plumber for
a free phone consultation. Then I'd call the plumbing inspector in my
city, county or state for more advice (second opinions are always
good). After that, I'd entertain the idea of buying the 100 gal heater
and plumbing it so that it is dedicated to the tub (which uses far
more water than the shower does, and certainly will when you start
bathing the baby everyday in the tub rather than the conventient sink
or portable baby tub - I mean, you can't put the little guy/gal in the
shower now can you?). This will leave the 50 gal tank to service the
shower. The only decision then is which one do you plan to service the
remainder of the house with. But honestly, it probably won't matter.
Just make sure that no one is trying to wash clothes while you're
taking a bath - but it sounds like you are probably doing that
already. The bottom line is you'll have a hundred more gallons of
scalding water at your disposal that you didn't have before and you
aren't likley to burn up a tank or a kid (or a mother-in-law) anytime
soon.

Oh, and get some faucets/nozzels that aireate or supress the water
flow. This will give you the feeling that you've increased your water
pressure while in reality it is actually regulating the amount of
water that is consumed at each batheing. You'll not only save water,
get a harder stream and use less hot water, you'll save bucks. The
money you can save in water and gas alone will make these little
gadgets pay for themselves in no time. Over a longer period of time
you may even recoup some of the extra money it cost you to buy the
bigger (and wiser) tank.

I am posting this as a comment rather than an answer because I cannot
answer your ideal hook-up question or your regulations question. Let's
just say that this falls in the "Anything else should I know?"
category. If you like this as answer, you can leave a comment to that
affect and I can post it as one and close your question.

Regards;
tutuzdad-ga

Hi terrymeca,

I am a Service Manager for a plumbing & heating service company...

There are also "High Output" HWT's that produce more hot water than
you can use per hour, ask about GPH ratings (gallons per hour). in
effect becoming the On Demand type water heater that is very expensive
to install. The High Output HWT's use more BTU's, have thicker
insulation and are very efficient. If you have room, I'd install a
second HWT near the jetted tub, for that bathroom only.

I HIGHLY recommend "Bradford-White" units.
http://www.bradfordwhite.com/

They are not available in Home Depot or Lowes, you must be a
contractor to purchase them. I have never seen one need service in a
year of working here. We repair all brands, and when a customer wants
a new tank, we replace other brands with the Bradford-White brand, and
I have never seen a service call come in on one. They are very, very
good.

--Cynthia