Sizing Guide

Guidelines for Sizing

  refers to the rate of flow in gallons per
minute (gpm) necessary to efficiently maintain the system.
The “Fixture Unit” method is suggested for determining this
figure. This approach assigns a relative value to each fixture or
group of fixtures normally encountered. Determination of the
required  is as follows:
 • List all fixtures involved in the installation and using
Figure 1, assign a Fixture Unit value to each. Add to
obtain total.
 • ReferringtoFigure2,locatethetotalFixtureUnitamount
along the horizontal axis of the graph and follow vertically
until intersecting the plotted line. Read the 
in gpm along the vertical axis.





Bathroom group, consisting of lavatory, bathtub
or shower and (direct flush) water closet
10
Bathroom group, consisting of lavatory, bathtub
or shower and (flush tank) water closet
6
Bathtubwith1-1/2"trap 2
Bathtubwith2"trap 3
Bidetwith1-1/2"trap 3
Dental unit or cuspidor 1
Drinking fountain 1
Dishwasher (domestic type) 2
Kitchen sink (domestic) 2
Kitchen sink (domestic with waste grinder) 3
Lavatorywith1-1/2"trap 1
Lavatory(barberorbeautyshop) 2
Laundrytray(2-compartment) 2
Shower stall 2
Shower (group), per head 3
Sink (service type with floor drain) 3
Sink (scullery) 4
Sink (surgeons) 3
Urinal (with flush valve) 8
Urinal (with flush tank) 4
Water closet (flush valve) 7
Water closet (flush tank) 3
Swimming pools (per 1000 gal. capacity) 1
Unlistedfixturewith1-1/4"trapsize 2
Unlistedfixturewith1-1/2"trapsize 3
Unlistedfixturewith2"trapsize 4
Unlistedfixturewith2-1/2"trapsize 5
Unlistedfixturewith3"trapsize 6
Unlistedfixturewith4"trapsize 7
Water softener (domestic) 4
Washing machine 2
TOTAL
Figure 1.

 is a combination of two components — Static Head
and Friction Head — and is expressed in feet (refer to Typical
Installation illustration, Figure 3).
 is the actual vertical distance measured from the
minimum water level in the Basin to the highest point in the
discharge piping.
 is the additional head created in the discharge
system due to resistance to flow within its components. All
straight pipe, fittings, valves, etc. have a friction factor which
must be considered. These friction factors are converted to,
and expressed as, equivalent feet of straight pipe, which can
then be totaled and translated to Friction Head depending on
the flow and pipe size. Basically, this is reduced to four steps.
1. It will be necessary to determine the discharge pipe size. In
order to ensure sufficient fluid velocity to carry solids, (generally
acceptedtobe2'persecond),flowsshouldbeatleast:
 •9gpmthrough1-1/4"pipe
 •13gpmthrough1-1/2"pipe
 •21gpmthrough2"pipe
 •30gpmthrough2-1/2"pipe
 •46gpmthrough3"pipe
2. The length of the discharge piping is measured from the
discharge opening of the pump to the point of final discharge,
following all contours and bends.
3. To determine the equivalent length of discharge piping rep-
resented by the various fittings and valves, refer to Figure
5 and total all values. Add this to the measured length of
discharge pipe and divide by 100 to determine the number
of100'increments.
4. Refer to Figure 4 and find the required  
(determinedfromFigure2).Followgallonsperminuteto
pipe size being used. Multiply this number by the number
of100'increments.
Add the Static Head and Friction Head to determine .
2
Figure 2.
200
100
90
80
70
60
50
40
30
20
10
10 20 30
40
50 60 8090
100
70 200 300 400 500 600