Fisher & Paykel DD603(I) Manual page 23
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Also See for DD603(I):
- User manual (32 pages) ,
- Accessory installation manual (12 pages) ,
- Service manual (47 pages)
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W
H
W
H
A
T
E
R
A
R
D
N
E
A
T
E
R
A
R
D
N
E
W
W
H
W
W
H
H
A
T
I
S
A
T
E
R
H
A
T
I
S
A
T
E
R
Hard water is water that contains dissolved chalk, lime and other minerals. Rainwater is naturally
soft, but when the water filters through the chalk and limestone, present in the ground. It can
dissolve some of the minerals and remains in solution. The solution contains salts of calcium and
magnesium like bicarbonates, chlorides and sulphates. The hardness of your water is dependant on
where you live and the source (river or ground water) of your main water supply.
Types Water Hardness
Hardness can be classified in two ways
1
With respect to the metallic ion
ie Calcium and Magnesium hardness.
Total Hardness = Calcium hardness + Magnesium Hardness
2
With respect to anions associated with the metallic ion.
The hardness can be either temporary or permanent hardness.
Temporary hardness can be removed by boiling the water. Permanent hardness cannot be
removed by boiling but by chemical treatment only.
Total Hardness = Non carbonate hardness + carbonate hardness
H
O(l) + CO
2
2
H
O(l) + CO
2
2
Permanent Hardness is caused by Calcium and/or Magnesium sulphate.
Aq. + CaSO
(s)
4
Aq. + MgSO
4
U
U
N
I
T
S
O
F
W
A
T
E
R
H
N
I
T
S
O
F
W
A
T
E
R
H
There are a number of ways of expressing water hardness.
Water hardness can be measured in part per million (ppm) or in milligrams per litre (mg/l). Both
these units are exactly the same.
following table.
Mg/l or ppm as
Calcium Carbonate
100
200
300
400
S
S
S
S
?
?
A
R
D
N
E
S
S
A
R
D
N
E
S
S
(g) + CaCo
(s)
3
(g) + MgCo
(s)
3
Ca
(s)
Mg
A
R
D
N
E
S
S
A
R
D
N
E
S
S
Other ways of measuring water hardness are shown in the
Degrees Clark or
English hardness
Ca(HCO
)
3
2
Mg(HCO
)
3
2
2+
2-
(aq) + SO
(aq)
4
2+
2-
(aq) + SO
(aq)
4
Degrees
German
(ºE)
(ºd)
7
5.6
14
11.2
21
16.8
28
22.4
Degrees
Grains/
French
Gallon
(ºF)
(gpg)
10
5.83
20
11.66
30
17.49
40
23.32
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