3" or 4" line to Septic Tank?

We are in the Process of installing a new Septic Tank and wanted people's opinions on if I should have a 3" line to the Tank or a 4" line to the tank?
I've heard that the 3" is 1/4" per foot Drop and with the steeper sides allows the solids to be carried away easier with less liquid. Clogs a bit more then a 4"
I'm heard that the 4" is 1/8" per foot Drop. With the shallower sides it would allow the liquid to run away from the solids much faster and would hardly ever clog.
So it seems like there are plusses and minuses to both. I'm going about 80' from the house to the tank and have the 1/4" drop that I would need for 4"
Suggestions? Comments?
Thanks!
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flow.
lee h
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lee houston wrote:

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every 20'???
Hmmm... Seems Excessive? We were thinking of one right at the exit of the home, then its pretty much a straight shot to the tank. Would look funny with 4 cleanouts sprinkled throughout the yard?
Thanks!

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Scott Townsend wrote:

Set a Bar-B-Que on the first, a rock garden on the second, and a bird-bath on the third.
You'll have a hard time going eighty feed with a fifty-foot snake.
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electric motor powered snakes from rental place can go 100 ft.
lee h
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LOL. Good one.
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Scott Townsend wrote:

Around here in northeast tennessee 4 inch is the minimum size you can run once you leave the house......ther is probably a reason for that ~:>
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Thanks Guys!! 4" it is.
Now for the Secondary Question... (-;
We are adding a Granny unit to the main house and they want us to have the main house tank drain into the Sump Tank for the New Granny unit, then pump both up to the leach field.
I have another 60-70' run that Will be from an Existing line of unknown size to a Sump Tank. Should that also be 4"? It only going to be the liquid from the second chamber of the primary tank.
We have yet to find the line, so thats why I dont know the size yet. I just wanted to make the hardware run today and get all the material.
Thanks again!

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Scott Townsend Wrote: > We are in the Process of installing a new Septic Tank and wanted > people's

Your slope or fall will be 20 at per foot. Try to dismiss this old debate of solids being left behind swiftly moving liquids. Concentrate on a true/consistent slope without bellies. Install at least 2 cleanouts with access at grade level. A 4 line will allow for future needs and improvements.
I would recommend 'ABS drain products' (http://www.plumbersurplus.com/Category.aspx?Cat52 ) such as these.
--
PSZach

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I would use 4" from the house to the tank, 3" for main lines inside the house. Remember to put a cleanout tee near the outside of the foundation for easy maintenance in the future.
3" is supposed to work better with today's low flow toilets, as a 4" pipe lets the smaller amount of water spread out too thin to carry the solids away. Of course, anything that does get left behind usually gets washed away with the next flush, laundry, shower, or sink usage...

1/4" per foot is about the ideal slope regardless of pipe size. But, you can get by with 1/8" per foot on larger pipe if you have longer distances to cover.
1/4" per foot would require about a 20 inch drop over your 80 feet.
1/8" per foot would only need about a 10 inch drop for the same 80 feet.
I'd still choose the 1/4" per foot slope if you have the height to accomodate it.
Anthony
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