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American Society of Heating and Ventilating Engineers Guide, 1935
would be sufficient; and that where the flow is 100 gpm in the riser branch and rise
5-in. size would be correct. Of course these are somewhat excessive flows and the h' h
from the tank is small so that large sizes are to be expected. It would be necessarvt
carry a 5-in. riser down to the branch to the top floor, then reduce to 4 in. for th
branch to the floor below the top, and below this the sizes in Table 2 could be followed
In such a case, flush tank closets should doubtless be substituted.
ed'
Friction Loss per 100 Ft Straight Pipe in Pounds per Square Inch
Fig. 3. Chart Giving Friction Losses for Various Rates of Flow of Water
still giving the same pressure at the top fixtures, would have been 0.43 lb X 10 ft or 4.3 lb greater and this, with the 1 lb drop used previously, would give a total allowable drop of
1 lb + 4.3.1b = 5.3 lb
which, divided by the 600 ft equivalent run gives a drop per 100 ft of
5.3 X 100 600
0.9 lb
and, with this drop, the sizes according to the chart (Fig. 3) are 6 in., 4 in., and 4 in-
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Chapter 35--Water Supply Piping
respectively, while if the run is reduced to 200 ft instead of 600 ft, the allowable drop will be 5.3 lb X 100 = 2.7 lb per 100 ft.
200
This gives 5 in-, 4 in., and 3 in:, respectively, for the flows of 400, 200, and 100. gpm.
Water Line
House Supply
House Tank-f'
Fire Reserve __ i_
-_______ _
r
199 4s - '
296 IF
199 4'
4W.C.-F.V. 2U.-F.V. 3 Lav.
202 4.
6W.C.-F.V 4 Lav.
-j--i 297 "
137 r! i&s.
X
.. 179 2i 7th. '
165 2" 6th.
,, 134 2 5th.
4W.C.-F.V. 2U.-F.V. 3 Lav. .
4W.C.-F.V. 2U.-F.V. . 3 Lav.
4 W. C.-F; V. 2U.-F.V. 3 Lav.
19 r 4th.
10 lav.
10 3rd. .
8 4"
2nd.
IS. S. 1S.S.
2C 6W.C.-F.V. 189 2 4 Lav.
I82 2"
6W.C.-F.V. 4 Lav.
*73 2"
6W.C-F.V. 4 Lav.
164 2
4W.C.-F.V. 2U.-F.V.
3 Lav.
. 149 2
4W.C.-F.V.
2U.-F.V. 3 Lav.
.. 2W.C.-F.V. 98 1? 1U.-F.V.
1 Lav.
136 2j 1 & & .
134 2" 1 S.S.
133 2' 1S.S.
3 W.C.-F.V. .131 2" 1 Lav.
, a 1 S. S.
129 2" 2 Uv.
127 *
3W.C-F.V. 1 Lav.
4 4' is.s,
50 It 1W.C.-F.V.
4 4 1SS.
1st
(I)
. (2)
(3)
Fig. 4. Typical Layout for Down-Feed System
From Example 3 it is evident that, while the down-feed system possesses certain economies in size for the riser portion, it is quite likely to involve large distribution main sizes, especially when the tank is not elevated to a considerable degree.
SIZING A PIPING SYSTEM
Example 4- Fig. 4 shows a typical layout with three risers extending eight stories and with the fixtures noted on each floor. First this will be solved for a down-feed arrange ment assuming that the level of the water in the house tank is 30 ft above the fixtures on
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