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Size of pipe to the Septic Tank?

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Size of pipe to the Septic Tank? Scott Townsend 08-25-2006
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Posted by Scott Townsend on August 25, 2006, 1:20 am
I have a 3" line from under the house. The guy I spoke with that does Septic
Systems says 4" no less.

My run is about 85' from my house to the Septic Tank. I have the 1/4" per
foot Fall from the House to the tank.

Should I upsize the pipe to 4" or just keep the 3"

I don't want my liquids to run from the Solid, so I though that the 3" would
be better?

Thanks!



Posted by buffalobill on August 25, 2006, 3:42 am
[is this for an existing or new system? is there a problem now?]
talk to your neighbors if they have similar lots and hills of pitch.
and the pump out sewage company. then your local plumbing permit office
and health department. plan piping in advance for a future municipal
hookup. always better to design properly when it comes to plumbing.
basics at:
http://en.wikipedia.org/wiki/Septic_tank
http://people.howstuffworks.com/sewer.htm


Scott Townsend wrote:
> I have a 3" line from under the house. The guy I spoke with that does Septic
> Systems says 4" no less.
>
> My run is about 85' from my house to the Septic Tank. I have the 1/4" per
> foot Fall from the House to the tank.
>
> Should I upsize the pipe to 4" or just keep the 3"
>
> I don't want my liquids to run from the Solid, so I though that the 3" would
> be better?
>
> Thanks!


Posted by Scott Townsend on August 25, 2006, 2:59 pm
Its a new house and new System. Well for the most part anyway... new 2nd
Dwelling, new lines, new tank, etc. Old tank will drain into new tank, which
will pump up to the field.

So my concern is more of the liquid running away from the solids. I've heard
that the 4" gives you the better flow, easier to clean, etc, but the 3"
makes it so your liquid level is higher to carry away the solids.

So with an 85' run @ 1/4" per foot drop, should I upsize from the house's
3" to 4" to the tank, or just leave it at 3"?

Thanks


> [is this for an existing or new system? is there a problem now?]
> talk to your neighbors if they have similar lots and hills of pitch.
> and the pump out sewage company. then your local plumbing permit office
> and health department. plan piping in advance for a future municipal
> hookup. always better to design properly when it comes to plumbing.
> basics at:
> http://en.wikipedia.org/wiki/Septic_tank
> http://people.howstuffworks.com/sewer.htm
>
>
> Scott Townsend wrote:
>> I have a 3" line from under the house. The guy I spoke with that does
>> Septic
>> Systems says 4" no less.
>>
>> My run is about 85' from my house to the Septic Tank. I have the 1/4" per
>> foot Fall from the House to the tank.
>>
>> Should I upsize the pipe to 4" or just keep the 3"
>>
>> I don't want my liquids to run from the Solid, so I though that the 3"
>> would
>> be better?
>>
>> Thanks!
>



Posted by Edwin Pawlowski on August 25, 2006, 11:25 pm

>
> So with an 85' run @ 1/4" per foot drop, should I upsize from the house's
> 3" to 4" to the tank, or just leave it at 3"?

I'd make it 4".

http://www.eng-tips.com/viewthread.cfm?qid=162208&page=1
http://www.howstuffworks.com/sewer2.htm

http://muextension.missouri.edu/explore/envqual/eq0401.htm
In all septic tanks, the inlet and outlet pipes should be at least 4-inch
diameter Schedule 40 PVC, cast-iron or other approved pipe and be protected
by baffles or sanitary tees made of acid-resistant concrete, acid-resistant
fiberglass or plastic.


http://www.deq.state.or.us/WQ/wqrules/Step3.pdf#search=%22septic%20system%20pipe%20size%22
?? Sewers shall be minimum 4" diameter, installed with tracer tape or toning
wire.

?? Sewers shall be designed to flow half full, based on 1 gpm per dwelling
and Manning's n = 0.013. Minimal

velocities are acceptable. However, low-velocity and flooded sections may
require sulfide controls.

?? Subject to a 4" minimum diameter, inverted siphons shall be designed to
flow at a velocity of 0.5 feet per second

or greater, based on a Hazen-Williams coefficient of 100.



Posted by Scott Townsend on August 26, 2006, 4:02 pm
Thanks for the info!!!

Scott<
>
>>
>> So with an 85' run @ 1/4" per foot drop, should I upsize from the
>> house's 3" to 4" to the tank, or just leave it at 3"?
>
> I'd make it 4".
>
> http://www.eng-tips.com/viewthread.cfm?qid=162208&page=1
> http://www.howstuffworks.com/sewer2.htm
>
> http://muextension.missouri.edu/explore/envqual/eq0401.htm
> In all septic tanks, the inlet and outlet pipes should be at least 4-inch
> diameter Schedule 40 PVC, cast-iron or other approved pipe and be
> protected by baffles or sanitary tees made of acid-resistant concrete,
> acid-resistant fiberglass or plastic.
>
>
>
http://www.deq.state.or.us/WQ/wqrules/Step3.pdf#search=%22septic%20system%20pipe%20size%22
> ?? Sewers shall be minimum 4" diameter, installed with tracer tape or
> toning wire.
>
> ?? Sewers shall be designed to flow half full, based on 1 gpm per dwelling
> and Manning's n = 0.013. Minimal
>
> velocities are acceptable. However, low-velocity and flooded sections may
> require sulfide controls.
>
> ?? Subject to a 4" minimum diameter, inverted siphons shall be designed to
> flow at a velocity of 0.5 feet per second
>
> or greater, based on a Hazen-Williams coefficient of 100.
>
>



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