Install Instructions

24
The usage of water softening equipment greatly reduces the
hardness of the water. However, this equipment does not
always remove all of the hardness (lime). For this reason
it is recommended that a regular schedule for deliming be
maintained.
The time between cleaning will vary from weeks to months
depending upon water conditions and usage. A change of
approximately 5
0
F in the normal temperature rise through the
heater is usually an indication that scale should be removed.
For long life, copper or brass is recommended for all valves, pipe
and ttings used between gate valves “A” and “B” and the heater,
see g. 17.
Heater failure due to excessive lime build-up voids the warranty
.FIGURE 16
DELIMING SOLVENTS
A. O. Smith recommends the use of UN•LIME
®
for deliming.
UN•LIME is a patented food grade acid which is safe to handle
and does not create the harmful fumes which are associated with
other products.
UN•LIME may be obtained from your dealer, distributor or the
A. O. Smith. Order part no. 9005416105 (1 gal.), packed 4 gallons
per case, or part no. 9005417105 (5 gal. container).
CAUTION
Observe handling instructions on label of product being used.
REMOVING LIGHT DEPOSITS
1. Shut off electric and gas supply to the burner.
2. Close gate valves “A” and “B”.
3. Install drain hose assembly in upper deliming tee. Open drain
cock and drain heater. Install standpipe in lower deliming tee
or in tee from which pressure relief valve has been removed.
4. Close drain valve.
5. Slowly pour 3 gallons of UN•LIME into heater through
standpipe. Direct solution into suitable container with a hose,
see g. 17.
DELIMING THE HW WATER HEATER
FIGURE 17
6. Continue to fill until foaming action stops.
7. When foaming action has stopped completely, allow 10 to
15 minutes for UN•LIME to dissolve any remaining scale
in the heater.
8. Open the drain valve and drain all UN•LIME from the
heater.
9. Remove standpipe and drain hose assembly from tees.
Install fittings originally removed into openings. Open
valve “A”, allowing fresh water to flow through heater and
out drain valve for 3 to 5 minutes.
10.Close drain valve and open valve “B”. Heater is now
ready for operation.
HEAVY LIME DEPOSITS
If the solvent does not readily pass through the clogged coils
or heat exchanger, it will be necessary to use a deliming
pump or contact a service agency for proper cleaning.
A. O. Smith Form No. 4778, entitled “All About Deliming Coil
Type Water Heaters”, describes heater cleaning methods
and equipment required. UN•LIME and the booklet may
be obtained through your dealer, distributor or A. O. Smith.
FIGURE 18