Question
QUESTION: I have had standing water issues as well as soggy areas every few years since I have owned my home.  Some years back I had a contractor install french drains to keep the water from coming into my basement and it worked well.  However, since my water table is high and we have underground springs, every few years some portion of my lawn has water when the springs change direction.  I have researched how to do the french drain my self and have dug a trench 60 X 12 feet to the previous french drain and have a decent pitch to make sure it flows in that direction.  Yet, I can't seem to get the water to flow in the direction I want.   Do you think I just need to continue to dredge the trench until it flows in the direction I want?  If the pitch was decent enough, shouldn't I see the water going in the direction I want after digging the trench and even before I lay the piping?

Any guidance would be appreciated!
Debbie

ANSWER: Hello,

Perhaps the problem is that the outlet for the pipes is not extending past the groundwater. If the entire structure of piping is sitting under groundwater than no positive drainage will take place. To drain groundwater,a herringbone or some other grid structure of piping is necessary,spaced according to soil type.

There could be several drainage solutions,depending on a drainage analysis of the property. A grid structure of drainage pipe is one of the most common approaches for draining groundwater but springs can sometimes make other methods necessary as they present a different set of problems than groundwater alone.

The water has to flow to some point. Where does the trench you dug lead to. If it leads to an area of more groundwater or an impervious layer of soil there will not be drainage. Good luck.

Mark Harshman
http://www.harshmandrafting.com
Email: [email protected]

http://www.scribd.com/markscrib47



---------- FOLLOW-UP ----------

QUESTION: Hello and thank you for your earlier reply.  At present, I have not placed the pipes in my trench.  I have been attempting to get the water to flow in the direction I want first.  That is toward the existing french drain that a contractor placed for me about 5 years ago.  I have begun the trench at about 6 inches and have dug about 18 -24 inches toward the direction I wish for it to go.  My research on the web tells me that with such a pitch it should flow in the direction I want.  However, it isn't and the trench has most of the water at the end I don't want.  I do not know if there are actually underground springs.  A neighbor was sharing with me that we had such.  I just can't seem to get the pitch right to get the water going in the direction I want.  My question is .......if the pitch is correct in the trench ( before I lay the pipes) shouldn't the water flow in the direction I want?  

Thank you once again!
Debbie

Answer
Hello,

Perhaps the problem is that the outlet for the pipes is not extending past the groundwater. If the entire structure of piping is sitting under groundwater than no positive drainage will take place. To drain groundwater,a herringbone or some other grid structure of piping is necessary,spaced according to soil type.

There could be several drainage solutions,depending on a drainage analysis of the property. A grid structure of drainage pipe is one of the most common approaches for draining groundwater but springs can sometimes make other methods necessary as they present a different set of problems than groundwater alone.

The water has to flow to some point. Where does the trench you dug lead to. If it leads to an area of more groundwater or an impervious layer of soil there will not be drainage.


The pitch should be a minimum of 1/4 inch per 1 foot. This means that for every 1 linear foot there should be a drop in elevation of 1/4 inch. Sometimes the pitch has to be greater to compensate for friction. The surface of a bare trench is not the same as the surface of a plastic,metal or concrete pipe. The pitch can be adjusted up higher to achieve different flow velocities. The flow velocity of a 1/4 inch in 1 foot pitch on bare soil will not be the same velocity as in a pipe. If possible,making the pitch somewhat greater will help clear out sediment but either too little or too much flow velocity is not desirable.

The existing french drains may not have the capacity to handle more water placed in them from the pipes you are proposing. As I mentioned earlier,if you have groundwater,take the traditional gridwork pipe structure approach. This is the same technique used to drain agricultural fields. Perhaps the french drains are clogged and have stopped working.

Determine the high point and low point of the pipe run and then fasten a string between these two points. Keep the grading even with the string.


Mark Harshman


For more comprehensive help check out my website at:

http://www.prestoexperts.com/expert/markland