Document daL92bGj3VNQE3Q10B0MLVjRq

. American Society of Heating and Ventilating Engineers Guide, 1934 and the pressure at the top of the required 15 lb will make the total reduction 49.4 lb, leaving a balance of 25.6 Id which may be used up in friction. If the distance from the Table 6. Typical Calculation of Pipe Sizes on Down-Feed Riser with Flush Valve Water-Closets and Urinals Riser No. S Floor of Bloc. Fixtures on Floor gpm PER Fixt. Max. Fixt. GPM Probable Use [per cent) Probable Fixt. gpm Probable Riser gpm Allowable Drop Lb per 100 ft Pipe Size In. 1st 2nd 1 S. S. 3 W. C. 1 Lav. 2 4 50 3 4 100 150 3 80 7 100 4 4 120 7 127 30 X 30 2 3rd 0 w. c. 0 3 2 Lav. 3 4 000 150 6 13 80 70 120 9 129 30 2 4th 3 W. C. 50 6 1 Lav. 1 S. S. 3 4 6 150 300 3 4 20 40 55 120 11 131 30 2 5th 0 W. C. 0 6 1 S. S. 4 7 000 300 4 24 40 53 120 13 133 30 2 6th ow.c. 0 6 1 S. S. 4 8 000 300 4 28 40 51 120 14 _ 134 30 2 7th 0 w. c. 0 6 1 S. S. 4 9 000 300 4 32 40 50 120 16 136 1 30 2H 8th 0 W. C. 0 6 1 s. s. 4 10 000 300 4 36 40 48 120 17 137 23 street main to the bottom of the riser, which will be assumed to be the farthest one on the horizontal line, is 100 ft, and if the fittings are sufficient to add another 100 ft, as well as the 80 ft of vertical distance up the riser, the total equivalent run will be 280 ft, which will be taken as even 300 ft. Then the allowable drop per 100 ft will be 25.61b X 100 or 8.5 lb 300 and the sizes shown in Fig. 5 are based on this amount of drop. Of course the other, 558 J Chapter 39--Water Supply Piping risers will have the same maximum flows at the bottom as they formerly had at the top, namely 202 and 137 gal, respectively, for Risers Nos. 2 and 3. Combining these maxi mum flows in the same manner as pursued in the down-feed system it is seen that the maximum flow between Riser No. 2 and Riser No. 3 is 296 gpm, and between Riser No. 3 and the street main, 297 gpm which at a drop of 8.5 lb gives the main sizes indicated. It will be noted that in determining the maximum flow in an up-feed riser Table 7. Size of Distribution Main for Down-Feed Systems. (See Fig. 4) Riser No. 1 2 3 Fixtures GPM PER Fixture 16 W. C. 8 U. 24 22 Lav. 3 S. S. 25 50 40 3 4 35 W. C. 5 U. 64 23 Lav. 48 50 40 3 6 W. C. 70 4 Lav. 6 S. S. 58 50 3 4 Maximum Fixture GPM 800 320 1120 66 12 78 1750 200 3070 69 147 300 3370 12 24 183 Probable Use (Per Cent) 15 40 8 35 7 33 Probable gpm 168 31 199 245 51 296 236 61 297 Allowable Drop (Lb per 100 Ft) Size of Main (Inches) 24 25 25 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. SIZINC 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 on account of the many plumbing fixtures having 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 in variably 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 follow: 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. 559 /