Concrete Pad Slope
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EddieWalker
Epic Contributor
Sewage lines are 3 to 7 percent slope with 5 percent being the easy number to keep things flowing nicely.
For an outdoor pad, I would want 2 to 3 percent. Water will stick to the concrete and not flow if it's too gentle a slope unless you have a lot of water coming down. Give it enough slope to get it away from the house.
Eddie
For an outdoor pad, I would want 2 to 3 percent. Water will stick to the concrete and not flow if it's too gentle a slope unless you have a lot of water coming down. Give it enough slope to get it away from the house.
Eddie
JB4310
Super Member
Around here sewers go down to 1% or 1.2" per 10 feet. To much pitch and the solids seperate from the liquid. only 4 inch house sewers have a minimum of 2%. Actually the large main trunk sewers are far less than 1%. they have to be, there's no way to maintain any more pitch in flat topographical areas. The treatment plant is 8 miles away but only 50 feet lower than here. At 5% you would only get 1/4 mile before that 50 feet would be used up.
But closed sewers are much different than slabs,
So as far as the pad goes I guess alot would depend on location, I imagine in sunny Florida even if the slab was dead level it would be dry 20 minutes after a rain. If the slab were in a harsh freezing environment then the higher end of the pitch recommendations here would be in order.
JB.
But closed sewers are much different than slabs,
So as far as the pad goes I guess alot would depend on location, I imagine in sunny Florida even if the slab was dead level it would be dry 20 minutes after a rain. If the slab were in a harsh freezing environment then the higher end of the pitch recommendations here would be in order.
JB.
JB4310
Super Member
I hate it when I make a level slab and the rain just piles up on it so I need waders!
Bruce
I formed up a little slab for my tractor shed, about an oversized 1 car garage.
Really just one form across the front at the apron, I fussed and fussed with it getting it just right. Then when the concrete truck came, he drove close to the form, with the ground being soft it heaved up about 2 inches. Of course I didn't realize it at the time. It ended up making the apron outside the door have the slightest reverse pitch.
I had to cut a small drain channel on one side, in the surface of my brand new slab
as I was worried the door might freeze down if water sat there.JB
EddieWalker
Epic Contributor
Your way off on your angle and your solids wouldn't move at 1%. There is some argument about the slope being too steep and the liquids out running the solids, but a lot of that is from the older type of pipes and not PVC.
You can have your treatment plant as far away as you want, and in most cities, even uphill from the sewage drains. The waste goes to a pump station where it is pumped up to a manhole, where it flows down to the next pump station or to the treatment plant.
Have you ever done sewage lines before? or are you using information that you heard second hand?
Eddie
JB4310
Super Member
WTF! Not to you Eddie
I just typed a long response to this and windows decided to run some update without even asking me, and shut down and lost my work.So anyway wife is screaming to get ready for church, but the short story is I do know a little about the subject and no our main trunk sewer has no pump stations.
Some pics of inside a large storm sewer.
JB.
Attachments
Same here. Any more than that and the water runs to fast leaving the solids.
1/8 per foot is more than enough pitch for an outdoor pad that has an even remotely decent finish job.
JB4310
Super Member
I know it's nothing to do with OP's pad but this explains how a sanitary sewer can flow for miles without much slope at all.
The 1% minimum is only for house sewer laterals that are 6 inch. 2% for 4 inch lines under the floor. once it gets into the street the slope requirements go way down. I guess it's due to the volume of push behind it?
See the chart on page 9, A 24" main sewer only needs 1 inch of slope for 100 feet!
http://www.co.rockbridge.va.us/departments/PSA/rules_regs/Section 2.pdf
JB
EddieWalker
Epic Contributor
OK, that makes more sense. I don't think we're talking about the same things with regards to the sewer lines. All I work on is residential remodels, and 2 percent might pass inspection, but it's gonna get me a real close look at everything else to make sure it's perfect.
Eddie
Eddie
