Question about foundation drains
Question about foundation drains
(OP)
I am a structural engineer and I have a question about foundation drains behind basement walls. Where does the water in those drains flow to? As a structural engineer we require that the soil behind basement walls be drained, but I am not sure who designs and documents the drainage systems behind basement walls - and where does that water flow to?
Are there any good articles or information on the internet that would be useful in further understanding the fundamentals of basement wall foundation drains?
Thank you in advance for any insight you can share on this.
Are there any good articles or information on the internet that would be useful in further understanding the fundamentals of basement wall foundation drains?
Thank you in advance for any insight you can share on this.





RE: Question about foundation drains
drainage outfall is
a) to sump pump
b) to sewer
c) to low outfall away from the bldg
RE: Question about foundation drains
RE: Question about foundation drains
As far as where to pump it to, if you can't send it to storm sewers ask if it can be pumped to the retention ponds. And sizing the system is a grey area, like cvg says. It's hard to get anyone to put anumber on the quantity of water coming out of a groundwater system. Luckily, the pumps are usually sized close enough that all you do is run them more if the design guessed wrong.
RE: Question about foundation drains
The county I work for does not allow new foundation drain connections to our storm sewers. One of our townships requires them. It has caused a few conflicts along our county routes in that town. It's best to check with the municipality(ies) involved.
Otherwise, you have to pump it to an infiltration drain, or to a rain garden, where some will infiltrate and some will transvaporate. I suppose you could use it for landscape irrigation or water features.
RE: Question about foundation drains
and by gray areas, I also meant that most structural / foundation engineers really do not care or know what to do. Cliff, you confirmed my suspicion in your reply. As a result, sometimes foundation drainage is not allways adequately designed. It is often left up to a contractor to design build and the results are often not adequate.
RE: Question about foundation drains
I have never come across a situation where the foundation drain is routed to the sanitary sewer.
The foundation drain is usually routed to the surface runoff, it can be routed to the storm drain if the municipality finds that solution acceptable.
RE: Question about foundation drains
RE: Question about foundation drains
RE: Question about foundation drains
RE: Question about foundation drains
RE: Question about foundation drains
http://www.eng-tips.com/threadminder.cfm?pid=256
This issue has been discussed there.
RE: Question about foundation drains
In an effort to solve a wet bsmt. problem around here, when they hadn’t bother to install drain tile on the outside in the first place, some folks do the following: They break out about 18" of the bsmt. slab all around, dig a trench down to the bottom of the ftg., place some gravel and a perforated drain tile in a geo-fabric sock, fill with gravel to the top of the ftg., tap all of the conc. blk. cores, install plastic tubes to drain over the tile, and finally replace the slab. This invariably happens during a wet period, when people have had it with the wet bsmt. Then the found. walls may sit in this laterally unsupported condition for at least 3-4 days, or longer, during the process. I’ve heard of instances where there were lateral found. movement problems with this. And, fly-by-night contractors who claim to know how to do this come out of the woodwork from time to time.
RE: Question about foundation drains
Without a soils report you are then designing to the max for everything structurally touching the ground, which seems like a huge waste of money.
B+W Engineering and Design
Los Angeles Civil Engineer and Structural Engineer
http://bwengr.com | http://bwstructuralengineer.com | http://bwcivilengineer.com
RE: Question about foundation drains
If you ask my opinion, i think the architect should own the drainage around the building and the Civil site egr should own it as soon as it starts getting piped away from the building.
RE: Question about foundation drains
RE: Question about foundation drains
If the site is producing a lot of pumped water this can become a nuisance, especially in the cold climates due to ice buildup.
Municipalities are encouraging civil engineers on new projects that will be pumping significant drain water (based on geotech soil report) to create a pipe network that connects to the storm sewer system.
Never connect these systems to the sanitary system, always the storm system.
These foundation sump flows are insignificant when compared to the storm sewer capacities. Therefore typically not even asked to document any flow rates, plan checkers just want to see the pipe network to check for typical interference issues. These municipalities field a lot of calls and complaints about the nuisance water, especially the ice buildup in the streets and sidewalks in the winter. They do no want to deal with this anymore so encourage developers to connect to the storm sewer.
RE: Question about foundation drains
RE: Question about foundation drains
RE: Question about foundation drains
If pumping is necessary for the structural integrity of the design, you must have backup electricity! Ground water seems to be the highest when the power is out. Blame Murphey.
I'd never use a foundation drain just as a supplement to bearing strength though. To limit demand on damp/water proofing, to reduce horizontal earth pressurs and to optimize the structural design of below-grade elements, sure.
f-d
¡papá gordo ain’t no madre flaca!
RE: Question about foundation drains