August 2, 2018

Best Practices for Zero Retaining Wall Failures - Venting of Drain Pipes Best Practices for SRW Design


To ensure there is no water buildup behind your retaining wall, drain pipes must be vented properly.  Drain pipes must exit to daylight or be connected to an underground drainage system. We recommend 4 in (10 cm) perforated flexible drain pipe or rigid perforated pipes.  When a rigid perforated pipe is used, it should be placed with holes down.

It is recommended that a minimum 1% gradient be maintained on the placement of the pipe with outlets on 50 ft (15 m) centers, or 100 ft (30 m) centers if the pipe is crowned between the outlets.

Also be sure that all pipe outlets be configured to be protected from crushing or plugging from other means.

Rodent screens are helpful to prevent nesting within the pipe. Cut adjoining block to allow for installation of a manufactured drain cover. Alternatively, Wall Drain Pro could be used without the requirement of cutting block. See more information here on Wall Drain Pro.


For more information on water management, check out sections 1.4 and 1.5 in the Allan Block Spec Book.  (ref. BP, Chapter 3.3)

Allan Block is working to achieve our industry initiative of Zero Wall Failures. With our Best Practices Manual and experience in the industry we are trying to expand the knowledge base for the design of segmental retaining walls (SRW's) by communicating and educating the professionals in the industry.  To see the full Best Practices Manual, visit allanblock.com to download today and keep an eye out for more industry Best Practice recommendations here.