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Distance from House to Septic Tank

BossHog's picture

Mom and Dad have been having some trouble with their septic tank lately, as well as with the pipe running from the house to the tank.

The pipe is probably 40 years old, and is full of tree roots. The tank is probably about as old. It has a cracked concrete lid, among other problems.

Dad was giving some thought to replacing it, and the question came up as to where to put a new one. He thought it should go about where it is - Roughly 30 feet (of pipe) from the house, right next to the garage, and right under a bunch of trees.

My thought was to run it 150' away, kinda downhill into an old pasture that's rarely used anymore. That way it would be easy to access when repairs or pumping were needed.

Dad said he didn't think the tank could be that far from the house. I don't see why it couldn't, as long as the pipe from the house to the tank had enough slope.

So what's the deal? Does the distance make a difference?

You're crazy enough for a post office job

(post #73674, reply #1 of 19)

Well, ya' know, "shid runs downhill . . ."

Does seem like a long way, though.  But, so is a sewer main - maybe upsize a little to get the right flow units, or whatever?  6" PVC?


(post #73674, reply #2 of 19)

I don't want to "call a professional" on you, but even here in rural Fillmore County MN, land of very few building inspections, septic systems are one of the few (along with well and electrical) that actually DO need to be inspected, and fortunately we have many good septic designers and builders that design and build to code.

Might I suggest you get one in your area involved now to help you out with the options?

(post #73674, reply #3 of 19)

It's a little early to call in a pro - This is mostly an idea at this point.

The question is a fairly general one about distance. We're not trying to design a entire septic system here.

A wise man will make more opportunities than he finds.

(post #73674, reply #4 of 19)

Well, then, I really think that distance is not an important factor, as long as the drainfield perks, and you have decent fall from house to tank to drain field.  I would love to have a nice level drainfield area like that within even a few hundred feet of my house.

(post #73674, reply #5 of 19)

"I don't want to "call a professional" on you, but even here in rural Fillmore County MN, land of very few building inspections, septic systems are one of the few (along with well and electrical) that actually DO need to be inspected, and fortunately we have many good septic designers and builders that design and build to code."

Hey, I was born and raised there (in Chatfield.)

I think Fillmore Co. is more careful than most about septic systems, because of the abundance of underground karst formations - there are so many caves and sinkholes around there, if you pour a cup of water on the ground who knows where it will end up.

(post #73674, reply #6 of 19)

Shoot, Ron, I've got a great idea !

Put your Sister's kids on it -  they'll have it fixed up in no time ! ! !

: > )


(post #73674, reply #7 of 19)

My septic people here in Iowa always tell me to keep the inbound line short & max 4% slope (1/4 in/foot). The outflow is low solids so slope can be steeper & much longer or even pumped up hill if from second overflow type tank.

If you have a problem, quit talking about it do something to fix it!

 Jim Andersen

Edited 9/1/2006 4:24 pm ET by jimcco

If you have a problem, don't just talk do something to set it right.

  Jim Andersen

(post #73674, reply #8 of 19)

You should keep the tank close to the house, but the D-box can be run quite a ways before it needs to supply the leach field. The outboard side of my tank went about 150' to the D-box before we had soil enough for the leach field.

The less line you have, the fewer places for it to go wrong when it's 20 below. Also, if the line will be driven over, you need to bury deeper or insulate it bec the road can make the frost go deeper. My exctvator told me about digging up a pipe that had frozen just where a dog ran along a fence on top of it.

Unless the tank is cracked, you shouldn't have to replace it. You can make a new lid easily enough. You can replace the root-bound pipe with plastic and not have to deal with future infestations.

Edit: What are the problems with the tank you mentioned? Has it been pumped?

Edited 9/1/2006 4:48 pm ET by splintergroupie

(post #73674, reply #9 of 19)

As a designer and regulator of septic systems, I've more typically had a problem with getting the tank far enough away from foundations, rather than keeping them close.   Typical regulations require the tank to be 10' to 20' from a foundation, which is to prevent weakening the foundation as well as preventing any overflow of sewage from wicking into the foundation and providing some room to service the tank.

 The sewer line from the house to the tank is more likely to clog than the line from the tank to the drainfield, for the obvious reason that what comes out of the tank doesn't have large solids (as others have pointed out).  So it does make sense to keep the building sewer shorter. 

But assuming that the sewer pipe has the correct amount of fall and is the correct diameter, there's no reason for the tank not to be as far from the house as is convenient.  Installing cleanouts in the sewer line is recommended, and may be required (here in VA they are required every 50 to 60 feet).

Avoid putting the tank under the bunch of trees.  There is a potential problem with tree roots invading the tank.  And the problem of excavating roots and killing the trees.

I applaud your foresight in choosing a location where the tank can be serviced.  Most of the homeowners I work with blow that off--until the tank needs to be pumped.  Then they whine about having to cut a hole in the deck, uproot landscaping, etc.




(post #73674, reply #10 of 19)

<<there's no reason for the tank not to be as far from the house as is convenient>>

This may be true in Virginia, but it's not true in my climate, where some people wrap the waste line with heat tape in case it gets bitter cold. I don't know how bad Boss's winter's get compared to yours or mine, but your experience may not hold true for him.

(post #73674, reply #11 of 19)

Well, freezing vs. not freezing is more a matter of depth, not distance.  That is, if there is potential for freezing a building sewer, you just have to be sure that the pipe has enough soil cover or other insulation to prevent freezing.  The potential of freezing in a building sewer installed with proper slope and bedding is less than for a water line, because you won't have any standing water in the sewer to freeze.  Of course, the vapor in the pipe could condense on the wall of the pipe and then freeze.

(post #73674, reply #12 of 19)

Here, the heat put off by the tank itself is a factor is keeping pipes from freezing. I just had two tanks pumped, one that never freezes about 10' from the house, and another wrapped in heat tape 75' from the house to be far enough away from a well head.

Tanks not used can actually just gets that cold and buring everything deeply enough to ensure nothing would ever freeze is impractical. Our water supply lines are buried a minimun of 6', and can still freeze under a road in an 'open' winter with little snow. Putting a layer of foamboard above the pipe after sand-bedding is a good solution, if a little spendy.

(post #73674, reply #13 of 19)

Yep, you're correct.  Friends that do similar work in Alaska talk about having to insulate septic tanks--which, as you point out, actually tend to emit heat.  Selecting the best answer for a given septic system problem usually boils down to weighing factors of cost and practicality against many possible solutions.  Like other building problems.

(post #73674, reply #15 of 19)

I don't remember hearing of a sewer or septic pipe freezing around here.

The coldest it's ever gotten that I can recall is about 20° below zero. Temps down to Zero are fairly common, but don't generally last for more than a few days. Our frost (footing) depth is 32".

Since this sewer pipe exits the house through the basement floor, I doubt there would be much danger of it ever freezing.

Everywhere is walking distance if you have the time.

(post #73674, reply #16 of 19)

Might work fine, but floating solids 150' is beyond my own comfort level.

(post #73674, reply #17 of 19)

Oregon is pretty strict about septic systems, although as the rules have been refined over the years, there has been improvement in groundwater and surface water quality along with more reliability of the systems themselves.

So here, in new construction or new septic systems, the tank must be 10' or more from a dwelling and must be accessable for service.  It should also be protected if it's located where heavy traffic or machinery might pass over it. (duh).

The field itself is designed by the Dept. of Environmental Quality and is based on site perk tests to determine the length and surface area of the field.  Size of the field is mostly dependent on the perkability of the soil and depth of groundwater.

In addition to the active drain field, in recent years, they've required construction of a "repair field" which are just additional laterals that lay idle until they may be activated if the active field fails.

And a house can be sited with 10' of the entire field.  Normally, the field is located at least 300' feet from any domestic water wells.

The last rule that comes to mind is that the drain field must be located where surface traffic of any kind is light.  Ideally, no part of it should be under a driveway or impervious surface, or in a pasture where livestock roam, etc. 



(post #73674, reply #18 of 19)

What everybody is saying about the solids is right. I've always tried to set the tank within a single run (20 ft.) of 4 in. PVC from the house. After the tank, it's just liquid. My last house in NJ was set up like that - Tank 20 ft. out, but the leachfield was 300 ft. further down the line.

Bigger issue is usually the distance between the tank and the well. In CT, that minimum is 75 ft. I think it's greater between the well and the field.


"Never try to teach a pig to sing. It wastes your time and annoys the pig." Robert A. Heinlein

"Get off your dead #### and on your dying feet." Mom


Senior Editor, Fine Homebuilding

(post #73674, reply #19 of 19)

Boss, my tank's a good 200-250' down the mountain.  1 cleanout that the health dept guy admitted would never be used.  Fall, I've got.  12 years here no problem.

As you point out, it won't freeze.  No worries.  I've got a pipe that's way above our footing depth in one place, has never frozen.

If you're gonna walk here by Tues., better get started.

PAHS Designer/Builder- Bury it!

PAHS works.  Bury it.

(post #73674, reply #14 of 19)

I wouldn't run 150' of pipe with solids in it at typical household flow rates.   An effluent line from tank to drainfield is fine, but not from house to tank.  Put it near the house, not more than 40-50' away. 

A septic tank replacement does not alwas have to involve a professional engineer or septic consultant, in my area it's considered a basic repair and comes in under the radar.   Check with your local building dept.