1.  The minerals the water softer uses to soften the water is salt.  That
actually leaves a little in the water and that's not supposed to be good for
you.

2.  My sister has a new A O Smith fiberglass lined water heater and she
purges hers once a month.  And it's just a water heater.  But Kankakee does
have 'hard' water.

Charles of Schaumburg

I would not feel comfortable using chemicals in a potable water supply
because there is no way to guarantee that you get it all out of the tank.

You mention water softeners, but from the context, I assume you mean water
heaters.  A water softener is supposed to remove mineral deposits; a water
heater heats the water.

If you have an electric water heater, the heating element is not underneath
the tank.  The heating elements are actually above the bottom of the tank so
that it does not sit in the sediment that builds up.

There is a sacrificial anode in the tank that corrodes so that the tank
itself does not corrode.

If you have a gas water heater, the flue pipe runs up the center of the tank
so that heat is transferred to the water through the center as well as from
the bottom.

Here is an explanation of how water heaters work:
http://home.howstuffworks.com/water-heater.htm

When you opened the drain your tank, did the water come out relatively
clear?  If you shut off the cold water supply and open the drain, the water
will drain very slowly unless there is a way to let air into the top of the
tank. I doubt if enough sediment built up on the bottom of the tank to clog
the drain valve, unless your water supply is really dirty.

If you want to empty the tank, shut off the heater so that you are not
heating an empty tank, shut off the cold water supply, and open the drain.
Then open a hot water faucet in the house to allow air into the top of the
tank, and it should drain much more quickly.

Glug-glug is because air has to enter the tank as water is released.  Open
the pressure release valve to add air to the tank as you empty the water.

You would be better served asking this question in alt.home.repair

If you are talking about a water heater and not a water softener, you
need to flush the tank yearly under pressure, not drain it. It is the
agitation of the water flow that will flush the tank bottom. Hook up a
hose to the boiler drain at the bottom of your tank and route it to a
drain. Open the valve and let it flush out under pressure for about one
minute. If you suspect heavy deposits, there are some commercial
products made that you can introduce into the tank to remove lime scale,
but an easy product to find at most stores comes to mind called "Iron
Out". It will remove lime scale and rust. If you have an electric
heater, lime scale will form on the heat elements as well, (usually two,
upper and lower) and the heating will not be as efficient as when they
are clean. They can be removed for cleaning or replacement if you must,
but that would not be normal. Try just flushing it first, then if you
need to, shut off the electrical and water supply to the tank, uncouple
at the di-electric fitting (cold supply, usually a blue plastic ring on
it), drain the water level down just a bit, and introduce the cleaner.
Let it work for about ten minutes or as directed, then couple up the
supply pipe that you disconnected, and flush under pressure. You may
need a few applications for a tank with heavy deposits. MAKE ABSOLUTELY
CERTAIN that you flush the tank VERY WELL after any chemical treatment.
Good luck.

 Are we talking softeners or heaters?  ;-)  Softeners put sodium ions
in the water that can precipitate out in the water heater, and add a
bit to the mineral buildup...

 Close...  On electric water heaters there are two calrod elements
sticking into the tank from the side near the top and bottom, and they
get coated, overheat, and fail early.  On a gas water heater, the
burner is under the tank, but the sides of the flue going up the
middle also contribute to the heating.

 The drain valve hole has crud in it - and/or they used a crap valve
with too small a hole.  Turn off the heater and allow it to cool, turn
off the water and relieve the pressure, and then take the drain valve
all the way off.  The loose crud will come out.

 Go buy a new Boiler Drain rated faucet, they have a seat that will
handle the heat.  Or better, a regular 1/2" ball valve, a brass nipple
into the tank fitting (to avoid dissimilar metals corrosion), and a
garden hose adapter.  They have "Quarter Master" ball valve faucets
that will work on hot water, but the orifice isn't full-flow sized.

 They put clean-out handholes on commercial water heaters so you can
reach in and scoop out the muck - but nobody ever does...

 It's regular steel, rolled and welded plate, stamped plate end caps
- pressure vessel.  They line it with baked on porcelain ("glass
lined") so it won't rust out as fast.  No banging on the tank, if the
lining cracks that's where the rust starts.  And Lime-Away is an acid
wash, shouldn't hurt anything.

 If your water goes cold fast, check the dip tube - the Cold inlet
has a plastic or metal pipe inside to carry the cold water down to the
bottom of the tank, so the rising hot water goes to the outlet.  If
the dip tube rusts off or breaks, the cold mixes at the top and the
hot striates and gets stuck at the bottom.

 The other thing to check, if you actually want to bother, is the
sacrificial magnesium anode - looks like a pipe plug on the side or
top of the tank, marked "Anode".  It's supposed to keep the cracks
from rusting by eroding first, and it works fine till it is used up.
If you find it chewed away, good luck finding a replacement - Plumbing
Wholesale House or Google for a supplier to ship you one.

 When the water heater finally dies, consider an "Instant" tankless
heater if you have gas - but get a good one rated for two major
appliances at once, especially if there are two or more people in the
house.  The 199KBTU or better input.  They cost a LOT up front, but
they save a lot of energy over their life, and will pay for
themselves.

 Electric tankless heaters will only work if you have an oversized
service panel - Yeah, Right, Suuure...  They use electric tankless
heaters as dishwasher boosters for restaurants - they draw 100A to
150A 240V 3-Phase.  That's why the building has a 1200-Amp service
panel.

 And if you are in an All Electric house, seriously consider changing
over to Propane for heating if you can't get natural gas (or even oil)
- there are way too many losses in electricity generation and
transmission, and you're paying for them.  Generate the heat directly
where it's needed, and you WILL save money.

     --<< Bruce >>--

Blocking the drain hole and too big to come out? Yes, that makes sense.

Flushing a water heater a couple times a year is usually a good idea.

That is if you dont end up causing more problems from desturbing
that 6 year old peice of junk plastic hose bib or end up with a seeping
presure relieve valve or something.

I would suggest just leaving the water heater alone because its probably getting a little
old and you may do more harm then good at this point. (unless it's gurgling real loud and bugging you.)

When it comes time to replace it then you can set up the new one with a good valve and whatever it needs
to make it easy to flush.   Remember you open that valve and you get HOT water blasting out of there at
the same pressure as the garden hose.

Dan