Rheem MPi 554 Series Owner's Manual And Installation Instructions page 13

CAUTION
If the water supply has a TDS greater than 150 mg/L and a green anode has not been changed to a black
anode, or if the TDS is greater than 600 mg/L and the anode has not been changed to a blue anode, there is
the possibility the anode may become overactive and hydrogen gas could accumulate in the top of the water
heater during long periods of no use. In areas where this is likely to occur, the installer should instruct the
householder on how to dissipate the gas safely.
If, under these conditions, the water heater has not been used for two or more weeks the following procedure
should be carried out before using any electrical appliances (automatic washing machines and dishwashers)
which are connected to the hot water supply.
The hydrogen, which is highly flammable, should be vented safely by opening a hot tap and allowing the
water to flow. There should be no smoking or naked flame near the tap whilst it is turned on. Any hydrogen
gas will be dissipated. This is indicated by an unusual spurting of the water from the tap. Once the water runs
freely, any hydrogen in the system will have been released.
SATURATION INDEX
The saturation index (SI) is used as a measure of the water‟s corrosive or scaling properties.
Where the saturation index is less than –1.0, the water is very corrosive and the Rheem warranty does not
apply to the water heater. In a corrosive water supply, the water can attack copper parts and cause them to
fail.
Where the saturation index exceeds +0.40, the water is very scaling and the Rheem warranty does not apply
to the water heater.
Water which is scaling may be treated with a water softening device to reduce the saturation index of the
water.
CHLORIDE AND PH
Where the chloride level exceeds 250 mg/L the Rheem warranty does not apply to the water heater. In a
high chloride water supply, the water can corrode stainless steel parts and cause them to fail.
Where the pH is less than 6.0 the Rheem warranty does not apply to the water heater. pH is a measure of
whether the water is alkaline or acid. In an acidic water supply, the water can attack stainless steel parts and
cause them to fail.
Water with a pH less than 6.0 may be treated to raise the pH. The water supply from a rainwater tank in a
metropolitan area is likely to be corrosive due to the dissolution of atmospheric contaminants.
SUMMARY OF WATER CHEMISTRY ADVICE AFFECTING WARRANTY
The water heater is not suitable for certain water chemistries. Those chemistries are listed below. If the water
heater is connected at any time to a water supply with the following water chemistry, the Rheem warranty will
not cover any resultant faults:
Water Chemistry
Total Dissolved Solids (TDS) > 2500 mg/L
Total Dissolved Solids (TDS) not suitable for anode type
Saturation Index (SI) < -1.0
Saturation Index (SI) > +0.4
Chloride > 250 mg/L
pH < 6.0
Component
water heater cylinder
water heater cylinder
water heater
water heater
water heater
water heater
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WATER SUPPLIES