Sometimes in these more wet climates contractors and long time homeowners throw around terms that not everyone knows. Not everyone knows what a foyer or powder bathroom is (it’s a large entry way and a bathroom without a shower), but people also don’t know what a French drain is. And no, it isn’t a drain with a funny accent.
As funny as it is to call a small bathroom a powder bath, maybe its as equally funny to call a trench with rocks in it a French drain. Afterall, that is kind of all it is, a trench with rocks in it. However, just like your powder bath would be a bad one without a light and a fan, a French drain wouldn’t be a good one without a perforated pipe and fall.
The application for French drains are probably pretty obvious. They just move unwanted water from one area to the other. If you have a soggy yard or a flooded crawl space we must have an efficient and reliable way to dry out the soil and keep it dry. In comes the proper drainage system.
If you spend any amount of time searching online on the proper depth, pipe, gravel type, location, and even color (yes color is argued) of French drains you will see there is absolutely no consensus. Shocking, I know, educated people on the internet with good arguments don’t agree on something. BUT! We are different in our approach because we have not been convinced that one method is better than the other. But of all the methods we do find that each one has its place.
EZ-Flow
EZ-Flow by NDS has great application as a crawl space drainage solution in our experience. However, we rarely use it in exterior drains for many reasons. Cost being a large one, it is 5x per foot than other applications, but it also is unpredictable in its ability to allow soil to settle around it. This might seem minor but no one wants their drain rock that is looking good in front of their home to look different or funky after that first heavy rain. And yes, in our experience EZ-Flow does in fact flow significantly more as the manufacturer advertises. I am not sure it is the whomping 30%, but it CLEARLY takes on more water and OBVIOUSLY runs cleaner. But we do not need to be as concerned about that in every scenario. Clean does matter when going into a sump pump. Into a drywell, maybe not so much…
Corrugated
The corrugated pipe wrapped in a filter fabric is the safest bet and is a big go to and rightfully so. It is our usual application for exterior pipe. But what about no fabric? That is likely a good option, which is real fighting words in this very niche world. When would you “risk” not using a filter fabric on a drain pipe? When you really need that sweet sweet flow baby! One less thing for the water to flow through does make a difference. It does come with careful application selection. But we have found that high clay soil, often times with a nice sod or high end dirt on the top layer makes this a good candidate for no filter fabric (usually referred to as a sock).
Say you have a nice yard that is very soggy but not quiet a sloppy mess. It could even be flooded but not a muddy mess. You dig down 6”-9” and the hole mostly keeps it shape, then it might be worth keeping the sock off. Afterall, the real filtering is done via the drain rock surrounding the pipe and it would be nice to get the extra flow. Someone is yelling and screaming “It’ll clog! It’ll clog!”. Yeah. It will. So clean it out. Big deal. You know what also clogs? Filter fabric. Which means that adding a clean out whenever possible without it being an eyesore is even more important.
The corrugated pipe really is the unsung hero for the French drain. The corrugation makes it flexible, which also broadens it’s application, but it also aids in cleaning and preventing clogs. As the pipe fills the corrugations cause the water to spiral and acts as a self cleaning process. It makes the pipe extremely durable and difficult to crush, a life saver for high traffic areas. It is easy to cut and extend in length for repairs, patching, and additions. Praise be for industrial plastics!
PVC and Triple Wall
PVC or Triple Wall pipe (the white pipe) is a far less common commonly used pipe for drainage in our experience. The price increase in minimal so I do not believe that is why, but it is definitely more difficult to work with. Whenever you need to make a turn you have to use an adapter which adds to the cost. These pipes seem to take on more water than corrugated pipes and I am lead to believe it is simply because it has larger holes. This pipe would be a terrible application for a high traffic area because it crushes easier and when crushed does not function nearly as well as a crushing corrugated pipe.
Applications where white pipe would be a good fit is where the water flooding is severe AND you do not need a sock. We have considered to start using this pipe for large soakage fields on the side of homes where you would run (3) 3” pipes next to each other to really move a lot of water in a straight line. It would be important to use a lot of rock and place these pipes pretty deep.
Down Spouts
This is just a friendly reminder that down spouts (buried and not) should never have perforated pipe near the home. Maybe when you get over 15’ away from the foundation you could switch to perforated to start dissipating the water but no closer. Down spouts do not feed into French drains. French drains have a pipe that is perforated (pipe with holes), in order to absorb water. A down spouts job is to take water captured by the gutters away from the foundation. Putting that water into a pipe with holes would be very counterproductive and likely flood your crawl space.
Summary
In summary there are a handful of different pipes you can use for your drainage and French drains. There are dozens of different application methods when you factor in placement, depth, discharge, rock type, filters, and so on. We do not believe one way is right. We do believe that different budgets, applications and goals warrant a certain type of French drain set up, of which we would love to discuss with you (for free).