Page 155 - Facility Piping Systems Handbook for Industrial, Commercial, and Healthcare Facilities

SOLID-LIQUID SEPARATION AND INTERCEPTORS

SOLID-LIQUID SEPARATION AND INTERCEPTORS 3.23

b. For medium-size shops and those with higher FOG potential, such as meat markets,
etc.—500 gal (1900 L) capacity
c. For large establishments, such as regular supermarkets—1000 gal (3800 L) capacity
d. For very large supermarkets and other similar establishments—1500 gal (5700 L)
capacity
5. A determination of the maximum possible flow rate shall be based on the following
table:
Drainage
Drain outlet or fixture fixture unit
trap size valve Peak flow per minute
in DN gpm DN

1 40 3 22.5 85
1 / 2
2 50 4 30 115
1 65 5 35 133
2 / 2
3 80 6 45 170
4 100 8 60 228
Dishwasher tank capacity gpm L
Up to 30-gal (115 L) water tank capacity 15 (57)
Up to 50-gal (190 L) water tank capacity 25 (95)
Up to 100-gal (380 L) water tank capacity 40 (152)
For restaurants, the size of the interceptor should be based on the number of seats and
the number of meals served, as indicated in Eq. (3.1). This formula is based on information
taken from the manual written by the EPA. This method was chosen because it appears to
have the most realistic sizing criteria of all methods examined.
×
DGL × HR × LF (3.1)
2
where D = number of seats in dining room
GL = 5 gal (20 L) of waste per meal served
HR = number of hours restaurant is open
LF = loading factor ∗
1.25 where located on interstate freeway
1.00 for other freeways and recreational areas
0.8 for main highway
0.5 for other highways (most often used regardless of location)
∗ The figure should be sufficient for most applications.
The recommended configuration of the interceptor shall be based on the following gen-
eral criteria. These recommendations should be adjusted to suit specific job conditions and
the selection of a specific interceptor.
1. 50 percent of the wetted height of the entire interceptor (both compartments) shall be
allowed for the storage of grease.
2. 6 to 12 in on the bottom shall be allowed for the accumulation of settled solids. The
smaller figure is usually applied to interceptors smaller than 1000 gal.
3. The invert of the inlet pipe shall be 6 to 12 in (152 to 300 mm) off the bottom, clear of the
settlement zone. An inlet baffle shall be provided, such as a tee facing sideways or other
acceptable method, to direct flow to the side of the interceptor and avoid short circuiting.

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