Drainage Help Needed!

   / Drainage Help Needed! #21  
</font><font color="blue" class="small">( So your saying water from the top of the hill flows down and fills up your septic system? )</font>

Since you have replied to my last post..... are you asking this question of me or the homeowner??? I have carefully read the homeowners situation as presented and am only commenting on a possible solution. /forums/images/graemlins/confused.gif

My suggestion was to help alleviate the rush of water down the hill toward the house. The terraces will help to stop this from happening. There is a certain amount of water that will reach the leaching area, since it is open to the rain and this cannot be prevented. The idea is to catch as much of the water from the problem area, and divert it to another area. I am not on site and I don't have a clue exactly where the leach field is located in relationship to the problem area. The final remedy must be made by the person that is on site and can view and take into consideration all the other aspects that will impact this plan.
 
   / Drainage Help Needed! #22  
lol im sorry junkman, i meant to hit reply but this forum is a little tricky for newbies like me. i actually like your idea very much so.
 
   / Drainage Help Needed!
  • Thread Starter
#23  
The actual leech field is way up at the top of the hill in question, so I don't worry about rain water with that. It is the holding tanks and pumping station that are right beside the house. If these weren't located right at that spot there would be enough room to make a large swale between the house and hill. But since they are located there you don't want to make that the low spot because then rain water can leak into the tanks and possibly overburden the pump and field. I started the terracing concept once but thought I would then have to build retaining walls and at that point it was only myself working on the project so I stopped that and switched to making the hill not quite so steep (I really need to take more current pics those are from April, I have moved quite abit of dirt with my handy boxgrader since then) of course I think I just move it around never really accomplishing anything. Put almost 100 hours on this tractor since I got it and don't really have alot to show for it.
 
   / Drainage Help Needed! #24  
When building a wooden 'something' they say measure twice, cut once. You need to slow down on the work, & plan plan plan. Sounds like you are going in circles right now, with no plan of what will actually help.

A 4" drain pipe is worthless. You needed 6" pipe to handle the eave drains, 8" if you are trying to handle the drains & the runoff from the hill as well. You were way, way undersized there.

You don't want terracing from the sounds of it, as you say you ripped out the one that was there & helping. So I won't suggest that. Well, not much, but you _NEED_ a little - see below.

Only leaves you wilth the drain pipe, really.

Can you change the eave drainage on your house at all? Can the upper side be piped over to the lower side of the house? Avoid putting any water to ground level on that side of the house if possible. If not, run a dedicated 6" pipe just as your current 4" pipe. The 6" will be able to keep up - the 4" never will.

Then a little farther away from the house, run a 6" perferated pipe in about the same manor. You can fill in the top of the trench, over the pipe, with gravel, crushed rock, or some such. You just simply need the dirt to be lower grade over this pipe than what it is closer to the house. You _must_ stop the water from rushing down the hill & smacking into the house. Either lower the ground over the drain pipe, or build a small berm (ridge) between the pipe & the house. Whatever it looks like, you just need to do this. Because the house was not planned & located well, "something has to give" and you are stuck with _needing_ this arrangement. No matter how much you are opposed to terracing, you either live with a wet house or put up with the looks of this. No getting away from it at this point.

Fill the trench over the perferated drain pipe with gravel, crushed rock, or the like. This will prevent water from moving through the dirt and into your basement - it will drain down & away before getting to your house. (This is a huge problem in houses situated where yours is - water can seep along soil layers from the top of the hill down to your house for weeks after a rain - will be a dry spell & you still have a wet basement! This drainage tile really should be as deep as the lowest floor or foundation bottom. You should be able to sue your general contractor for not installing such in the beginning - major error of design. Your house was built at the exact best location for a natural spring - should have been good drainage designed into the original plan, surprised you got a permit with no drainage provisions.) It will also allow your surface water to quickly perk down to the drain tile & soak into the pipe. But the gravel/rock would be mostly for draining sub-surface water seeping down the hill.

If you have a low spot, put a surface drain in. Run a 4" or 6" pipe up to the surface from your perferated pipe so the water can quickly drain away from your back yard.

For gosh sakes, get some vegetation on that hill! Seed something now, some type of grass. It will slow the water, use some water, help you as much as the drain tile will! /forums/images/graemlins/smile.gif


1. So, you need to adjust the berm/ swale a little bit. (I'm not really sure where your berm/swale deal is right now, since you said you took one out, moved a lot of dirt, & don't like the looks of these... Pictures are dark & old, so I'm just assuming you need to design such back in.)
2. You need to greatly expand the scope of your drain tile - (2) 6" or (1) 8" perferated tile at a minumum. One really should be burried at the bottom level of your basement foundation to protect the house from hydraulic pressures...
3. You need to have surface inlets, and/or gravel fill over the perferated tile to allow the water to soak into the tile.
4. You need vegetation (grass) covering the bare dirt.


Now, there can be local issues that make this entire plan have problems, but in general you need to do all this to keep your house dry.

--->Paul
 
   / Drainage Help Needed! #25  
You can put extensions on the septic tank and pump tank to bring the top up higher. Years ago I did this and at the time the connections were sealed with tar. Perhaps today they use gaskets?
But I have to ask - Who is responsible for putting the house in a hole? Dealing with water around a house is one of THE most important things to consider before a single shovel of dirt is dug.
If you are the one responsible then you can fix it however if the excavator or architect screwed up then get them to fix it.
And I agree that the (1) 4" pipe is way too small. We have (5) 4" pipes that take the water away from the gutters, etc.
And in a very heavy rain they get full.
I also agree that the corrugated pipe is not nearly as good as the smooth PVC pipe.
Also consider using schedule 40 PVC pipe as opposed to the thinner walled drain pipe.
If you think that anytime in the next 100 years or so that a heavy vehicle may drive over the area above the pipes you will never have to worry about sched 40 getting crushed. It may be overkill if the pipe is 2' underground but while you are at it - do the best job.

Good Luck,
Rich
 
   / Drainage Help Needed! #26  
I think Rambler hit it on the head. 4" pipe is definitely too small. 6" would help, but I'd be thinking hard about 8" or bigger. With more slope you can get away with smaller pipe sometimes.
 
   / Drainage Help Needed! #27  
additional 4" pipes are less expensive than one larger pipe and there is less resistance to flow with more pipes.... Just my opinion. 2 4" pipes will carry more than 1 6" pipe... 2 4" pipes are equal to 1 8" pipe.. double the diameter and increase the volume by 4.... /forums/images/graemlins/grin.gif
 
   / Drainage Help Needed!
  • Thread Starter
#28  
Paul, first off we can't sue ourselves since we were the general contractor and have built many previous houses. The house has drain tile installed around the perimiter of the foundation, it is a buried basement and the draintile drains into a sump pump that is pumped away from the house.

Second, the problem isn't a leaky basement, I don't have trouble with water in the basement (except when someone covered up the outside stairwells drain /forums/images/graemlins/tongue.gif) I tarred those walls myself and I put plenty on so as of yet the water has not gotten through. I just don't like seeing it really wet along side the house when it has been raining.

Third, complete agreement on needing a plan and grass /forums/images/graemlins/grin.gif I might plant a seed mixture that I have already for now. But the front yard will be getting the zoysia seed that now can't be planted until next spring.

I like the terracing idea and maybe you can make several small ones without having to make a retaining wall, the retaining wall is what deterred me.

Fourth, the house was placed in this hole because I didn't want the house at the top of the hill right beside the vet building, the driveway was already partially in down on this end (stupid reason I know) and since the garage is on the low end, the further we could get the right side in the ground the less stairs I would have to go up from the garage to get into the house. As it is now to keep the roof lines the same the garage walls are something like 14ft high and that is on top of the 2ft cement and brick foundation walls. Shooting the grade today, we think we have it figured out and with over 100" of fall from the corner of the house to the ditch I think it should flow pretty well. Thanks for your help and suggestions guys!
 
   / Drainage Help Needed! #29  
</font><font color="blue" class="small">( additional 4" pipes are less expensive than one larger pipe and there is less resistance to flow with more pipes.... Just my opinion. 2 4" pipes will carry more than 1 6" pipe... 2 4" pipes are equal to 1 8" pipe.. double the diameter and increase the volume by 4.... /forums/images/graemlins/grin.gif )</font>

Uh, no.

All other things being equal, a six inch line will carry about three times the flow of a four inch, and an eight inch will carry about six times as much.

Flow is a function of the pipe's area, it's wetted perimeter, and the roughness of the wall. We use a concept called the hydraulic radius, which is the area divided by the wetted perimeter, to account for the relation between skin friction and. the pipe diameter

The usual way to calculate flow in sewers and drains is with Manning's Equation:

Q = 1.486/n R^2/3 S^1/2

Q = flow in cubic feet / sec (CFS)
R = Hydraulic Radius ( = area / perimeter) in feet
S = slope in ft / ft
n = a coefficient of roughness (looked up from a table)

for smooth PVC n = about 0.010
for corrugated polyethylene n = about 0.022
for concrete pipe n = about .012

So first of all, you can see that smooth wall pipe will carry about twice as much (.022 / .010) as corrugated stuff of the same diameter.

Just to crunch some numbers, using an n value of 0.010 for smooth wall PVC, and a slope of 0.01 (1%), we get the following values for pipes flowing full.

4" pipe Q = 0.25 CFS
6" pipe Q = 0.73 CFS
8" pipe Q = 1.57 CFS.

There are other energy losses to consider, like bends, inlet losses, and outlet losses, but this is good enough for many applications.

This equation also works for flow in open channels like ditches or partially filled pipes, but the solution becomes more complicated than for pipes flowing full, usually requiring a trial and error solution, or a computer.
 
   / Drainage Help Needed! #30  
</font><font color="blue" class="small">( additional 4" pipes are less expensive than one larger pipe and there is less resistance to flow with more pipes.... Just my opinion. 2 4" pipes will carry more than 1 6" pipe... 2 4" pipes are equal to 1 8" pipe.. double the diameter and increase the volume by 4.... /forums/images/graemlins/grin.gif )</font>

Well, Dennis said what I was going to say, but he said it a lot better. You need to multiply by pi, so as his figures show, (2) 4" pipes actually carry less than one 6" pipe. As such, a bigger pipe is always cheaper than using multiple smaller pipes to carry the same amount of water....

--->Paul
 

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