Quick Reference Guide

UNT-PRC015-EN 7
Know the Riser Design—Design Return versus Reverse Return
• Higher cost and complexity—An additional riser pipe is required for each riser column (one
additional pipe for a 2-pipe system and two additional pipes for a 4-pipe system).
• There is additional complexity with the riser design and installation:
– The supply-side risers will begin with the larger diameter riser at the bottom of the column
and the smaller diameter riser at the top.
– The return-side risers will begin with the smaller diameter riser at the top of the column and
the largest diameter riser at the bottom.
– These details make the reverse return riser system difficult to coordinate during
construction.
Be sure all competitors are bidding the same riser system design to avoid an uncompetitive price
bid. The direct return method is usually preferred.
Figure 3. System 2—Reverse Return Figure 4. System 3—Reverse Return
4TH FLOOR
2ND FLOOR
3RD FLOOR
1ST FLOOR
BASEMENT
MAINS
R
S
REVERSE
RETURN
ROOF
SYSTEM 2 – REVERSE RETURN
2-pipe example
•
•
•
S
BASEMENT
1ST FLOOR
2ND FLOOR
3RD FLOOR
4TH FLOOR
ROOF
R
S
MAINS
SYSTEM 3 – REVERSE RETURN
2-pipe example