Document KRmyqbp6yYryLaxQbBVxQrX12

u/ American Society of Heating and Ventilating Engineers Guide, 1937 Table 6. Typical Calculation of Pipe Sizes on Down-Feed Riser with Flush Valve Water-Closets and Urinals (Riser No. 2. Fig. 4) Floor of Bldg. 1st 2nd Fixtures on Fux>r 1 w. c. 2 W. C. 3 U. 1 Lav. Gpm PER Fixture 45 45 30 3 Maximum Gpm on Floor 45 90 30 3 Maximum Gpm ON Riser Probable Use (per cent; 45 100 Probable Demand Riser Gpm 45 Allowable Drop Lb per 100 Ft 30 Pipe Size In. 123 168 58 98 3rd 4 W. C. 2 U. 3 Lav. 45 30 3 180 60 9 30 1 % 4th 4 W. C. 2 U. 3 Lav. 45 30 3 249 180 60 9 417 31 130 30 2 -------------- 5th 6 W. C. 4 Lav. 45 3 249 270 12 666 24 160 30 2 -- 6th 6 W. C. 4 Lav. 45 3 282 270 12 948 19 180 30 2 -------------- - 7th 6 W. C. 4 Lav. 45 3 282 270 12 1230 16 396 30 2H 8th 6 W. C. 4 Lav. 45 3 282 1512 270 12 282 . 1794 14 211 12 215 30 2X 24 Then the allowable drop per 100 ft will be 25.6 1b X 3o0u0u 100 = 8.5 lb and the s!izes shown in.Fig. 5 are based on this amount of drop. Of course the other risers will have the same maximum flows at the bottom as they formerly had at the top, namely 215 and 122 gal, respectively, for Risers Nos. 2 and 3. Combining these maximum flows in the same man ner as pursued in the down-feed system it is seen that the maximum flow between Riser No. 2 and Riser No. 3 is 255 gpm, and between Riser No. 3 and the street main, 282 gpm which at a drop of 8.5 lb gives the main sizes indicated. It will be noted that in determin ing the maximum flow in an up-feed riser it is necessary to begin at the top floor and work down instead of beginning at the bottom floor and working up as was done in the down-feed sizing. Chapter 35--Water Supply Piping and Water Heating Table 7. Typical Calculation of Pipe Sizes on Down-Feed Riser with Flush Valve Water-Closets and Urinals (Riser No. S. Fig. 4) __ -- Floor of BLDG. Fixtures on Floor 1st 1 S. S. 2nd 3 W. C. 1 Lav. 3rd 2 Lav. 4th 3 W. C. 1 Lav. 1 S. S. 5th 1 s. s. 6tb 1 s. s. 7th 1 s. s. 8th ' 1 s. s. Gpm per Fixture 4 45 3 3 45 3 4 4 4 4 %4 Maximum Gpm on Floor 4 Maximum Gpm on Riser Probable Use (per cent) Probable Demand Riser Gpm 4 100 4 Allowable Drop Lb per 100 Ft 30 135 3 138 142 63 6 148 . 61 . 89 90 30 30 135 3 4 142 290 4 294 4 298 4 . 302 4 306 41 41 ; 40 40 40 119' 120 120 121 122 30 30 30 30 2 Pipe Size In. H 1M 1M i 2 2 2 2 3 required that a gravity circulation be kept up in such hot water lines and this often has a considerable influence on the size. There are three methods of arranging circulation lines, as follows: . 1. By using the plain up-feed with a return carried back from the top of the riser and paralleling it. 2. By carrying a supply riser up in one location thus supplying fixtures on up-feed, then crossing over at the top and coming down past another collection of fixtures and supplying these by a down-feed. 3. By carrying all of the water to the top of the building and dropping risers wherever needed, feeding all hot water on a down-feed system. > Table 8: Size of Distribution Main for Down-Feed Systems (See Fig. 4) Riser No. 1 2 3 Maximum Gpm Riser 1038 1794 306 Maximum Gpm Main 1038 2832 3138 Probable Use (per cent) 18 9 9 : Probable Gpm Allowable Drop Lb per 100 Ft 187 255 282 2 2 2 Sub of Main In. * ' 4 4 5 j *s I, j | f | j I f | j j f J i * SIZING UP-FEED AND DOWN-FEED HOT WATER SYSTEMS Hot water supply systems, when of the circulating type, have a few differences to be-considered although the same general principles of sizing apply to these lines as to the cold water lines. Owing to the fact that .there are no flush valves'on the hot water piping and also because many plumbing fixtures have no hot water connections, the sizes of the hot water piping in general will be considerably less than the cold water piping in the same building. On the other hand it is almost invariably 656 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 ip the basement .and connected through a check valve, set on a 45-deg angle, and a gate valve; these return circu lation lines should nevec.be less 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 Tig. 6. 657 J\