Document nN5aj0Bb0qBX9wEL0eNX2Jn0G
American Society of Heating and. Ventilating Engineers Guide, 1934
Table 8. Typical Calculation of Pipe Sizes on Down-Feed Risers with Flush Tank Water-Closets and Urinals on Top Floor Only
Bldg.
Floor
gpm PER Fixt.
Max. Fixt.
gpm
Probable Use
(per cent)
Probable Use
gpm
Probable Riser gpm
Allowable Drop
Lb per 100 ft
7th and below
12 W. C. 6 U.
18 19 Lav. 3 S. S.
22
8th 0 w. c.
0 U.
18 4 W. C. 2 U. . 3 Lav.
31
50
40
3 4
00 00
18 18
3
Riser No. 1
600 240
840 18 i ; 151
57 12
69 40 | 28
000 000
840 18 72 36 9
186 37
151 69
179 220
30 '2H 3.3 4
7th and below
29 W. C. 5 U.
%A
19 Lav.
8 th
0 w. c.
0 U.
34 6 W. C. 4 Lav.
29
50 40
3
00 00
18 3
Riser No. 2
1450 200
1650 57
000 000
1650 108 12
177
10 42
10 38
165 24
165 67
189 232
30. 2*4 3.3 4'
7th and below
6 W. C.
5 S. S. 4 Lav.
9
8th 0 w. c.
6 I S. S.
10
50 4
*3
00 4
Riser No. S
300 40
20 12
32 50
120 16
000
300 40 4
120
36 48
17
--
560
136 137
30 2K 3.3 3
J
Chapter 39--Water Supply Piping'
The last method is usually the most satisfactory. (See Fig. 6). In the first instance the up-feed riser may be sized for the same pressure drop as used for the cold water riser and, from the top of the riser just below the top fixture connection, a return circulation line may be carried back to the main return line in the basement and connected through a check valve set on a 45-deg angle and a gate ;valve; these return circu lation lines should never beless than % in., and on the farther half of the risers, not less than 1 in. to favor circulation in the far end. Typical top and bottom connections for such risers are shown in Fig. 7.
8th. 7th. 6th. 5th.
4W.C.-F.V. 2U.-F.V. > 3 Lav.
. 4W.C.-F.V. 2l 2U.-F.V.
JL 3Lav-
,, 4W.C.-F.V. 2U.-F.V.
^ 3Uv*
,. 4W.C.-F.V. 2i 2U.-F.V.
) 3 Lav.
3" 10 lav. 4th.
3" 1S.S. 3rd.
3" 1S.S. 2nd
3' 1S.S. 1st
r 3" Main
(1)
Fig. 5. Up-Feed System
For the second arrangement of hot water risers, circulation lines are run back from the last fixture supplied to the main return circulation line in the same manner as just described, using % in. for the near risers and 1 in. for the far risers. The sizing is much more difficult, as it is necessary to start at the bottom floor of the return riser and work back to the top of this riser and then carry the maximum flow across onto the top of the corresponding supply riser and work down on this riser from the top floor to the bottom. Naturally this gives a much greater flow in the supply riser and aids circulation by reducing pipe friction. The allowable loss per 100 ft in such lines must be made about half that used for the cold
561