Septic line distance limitations

[5030tinkerer]

I will be building a new home and separate outbuilding this starting this spring. I'd like to put a half bath in the outbuilding. Does anyone know the feasibility of tying the outbuilding to the house septic tank? I suppose the real question is whether there is a distance limit I need to stay within for my drain pipe. I'd hate to have to put in two septic systems just for a convenience. /forums/images/graemlins/confused.gif

Thanks for any ideas,

Ed

 

[Bird]

Ed, I think I'd only be concerned with whether it was a distance that would permit me to keep a very slight downhill run to the septic system. Maybe someone else can refresh my memory; was it one inch or a quarter inch per 10' of lateral line? And there's another possibility also that you might consider, or talk to septic installers in your area. One of my brothers built a home on 10 acres and had one of the aerobic sewer systems installed at the time. Later, they fixed an RV parking site for the other brother to live on. The RV was about 75' from the septic tank, so the guy who installed the original system installed a 50 gallon underground tank with a macerator pump and a 2" line to the original septic system. Of course you'd have to wire the electric power for the pump, but it worked well for them.

 

[KentT]

I'm planning something similar, and hope to start construction soon -- it's still in the plans/blueprint stage. I'll be building a 2-car garage with an apartment over it, and a laundry room and 1/2 bath on the ground floor, to use a vacation cottage. Then, I plan to build a 3 BR retirement house a few years down the road, and connect the two with a covered breezeway.

I know of no distance limitations, as long as you can get sufficient grade, as Bird discussed. But, be sure to size the tank and field lines for the total needs of both buildings.

 

[5030tinkerer]

Thanks guys. TBN is truly awesome. Where else can you post a question before a late dinner and get a response when you get back to the ol' PC? I think I have the 1/4" drop per 10' run, but will verify when I get that far. For now, Bird has come up with an option that I hadn't considered that will surely work without a hitch. Am I correct in thinking that I'd want to bury that 2" line from the 50 gal tank to the main septic 42" down since a check valve just after the pump would possibly be keeping the line full all the time if it had to go uphill (or is there some other trick there)? The only concern that I would have about that is at the end of the 2" run (at the tie in to the 4" line from the house) since that would reasonably have to go uphill to make the connection. I suppose that I could just bury my holding tank such that the top is 42" or more down, thus requiring the 4" house feed line to be that low? Any drawbacks to this approach?

 

[inveresk]

I don't believe there is a regulation limit on lengths of drains to septic tanks provided you respect the 1 " 40 fall and have rodding eyes every 60 feet or so to clear blockages but you'll want to keep it as short as possible for maintenance purposes. The longer the run the deeper your drains will have to be in flat ground to get a gravity feed and there will be a limit on how deep you'd want to install you're septic tank.

The suggestion of installing a macerator by Bird is a good one that will ensure that any solids are at least part liquidised and if you can ensure a gravity feed to the septic tank, you shouldn't have much problems. Pumping is possible as well but best to try to design a gravity system first and turn to this option if gravity can't be made to work.

 

[TCarey]

Most plumbing codes require a minimum of 1/8" per foot of slope. That means every 96 feet of run, you will have 1 foot of fall. There really is no "limit" on the length of run, but you must maintain the fall. As mentioned earlier, every 75 feet code will require a cleanout be installed to clean the line if/and or when necessary.

If you cannot maintain the constant slope, you can go to a sewage lift pump and then you do not have to have that line at a gradual slope. The lift pumps will work OK, but anytime you can have a sanitary line drain naturally, you are better off than pumping.....

 

[PILOON]

Another option to consider is a second tank and a simple 'grey water' pump into 2" line feeding the drainage field.
That is if you have to go 'uphill'.
Such a pump is cheaper and easier to maintain than a solids pump.
I have 2 installations where I pump uphill as much as 25' to the drainage fields.
This is done in order to respect drainfield seperation from waterfronts.
Both pumping installations are reaching 20 yrs of operation.
Check valves are recommended otherwise backflow can actually damage the pump.
Usual installation calls for a greywater holding or pumping tank which can be even a large HD garbage plastic pail.

 

[tawilson]

I was at the plumbing supply house the other day, and they had on display a toilet setup with the pump built in. It's focus was on basement installations, but could be handy for many applications.

 

[Dmace]

Up here in NH, the rules are:

2% minimum slope from house to distribution box,
7% maximum unless you run a velocity reducer in the box, then it's 15% max.

There are no restrictions on length and the recommended pipe is 2" schedule 40 PVC pipe.

If you can't keep the pipe underground for the minimum slope for the entire length to the septic tank, then you could just gravity feed the line from the house to a 4x4 pump box. The box is 4' diameter and 4' deep, with a 1/3 - 1/2 hp effluent pump that pumps up to the d-box. There are limitations on length of a pump line, but that is all dependent on the head in the pump box and the friction loss in the line itself.

I have the charts for line friction and pump capacity if you need them.

I guess I should mention I am a septic designer also. /forums/images/graemlins/wink.gif

 

[EddieWalker]

I wouldn't use 2 inch pipe for draining anything but just water. If your running solids, as in a toilet, than use 3 inch line as a minimum.

Distance isn't an issue, but like everyone else said, drop is. You didn't mention how far this would be, but if you can tie into your existing system, than that would be cheapest and easiest.

3 to 7 percent is what I've always been told, but I wont' argue with 2 percent, but it seems on the shallow side.

I use a 6 foot level with a small piece of 2x4 taped to the end on it's edge. The level is 72 inches, so the 3 1/2 inch drop will put you real close to 5 percent.

How deep is the inlet to your septic? How far do you have to run the line?

If your 100 feet away, than your septic inlet needs to be between 3 to 7 feet deep with five feet giving you a nice 5 percent grade.

As for distance, the rule of thumb is to put cleanouts at just under twice the distance you can reach with a snake. My water utility is requireing me to put man holes in every 500 feet because they can reach 250 feet.

Will you ever have or need to dump an RV?

If you can, I like to have a cleanout on either end of the building so I don't have to take off the toilet to unplug a clog.

If you have to put in a collection tank and pump it uphill, there are kits to handle this. Allot of basements have this type of system. The size of the discharge pipe will based on the pump you use. I'd guess around an inch for what you need. My RV park will have a 3 inch line to handle the discharge for 300 RV's. Sewage under preasure requires a much smaller pipe than one fed by gravity.

Eddie

 

[Highbeam]

Gravity flow = 4" or bigger. Pressure flow can be as little as one inch, even a garden hose, if the pump is a grinder but 2" is recommended if using a transfer type pump. The problem with using too large of a line for the pressure system is terd jerkey. You need a certain flow velocity, 2 fps, once per day to blow out the sewage milkshake to prevent terd jerkey. Grinder pumps make a milkshake so this is more important than with a transfer pump which leaves the solids more intact. I would recommend the transfer pump with the 2" pressure line at minimum depth.

 

[Dmace]

I am taking this info straight from the NH Septic Designers Engineering Manual that I have used to design septics for over 5 years. You can not run more than a 15% slope to the septic tank. If you do it will cause "stirring". In a septic tank the effluent with settle and the solids turn to sludge that slowly deteriates with bacteria and the "water" overflows to the leach bed. If you cause "stirring" by having a pipe too steep, then the sludge will not settle and it will clog up and ruin your leach bed.

You shouldn't run more than 7% to the d-box. Even with a "T" style velocity reducer it can still skip through and cause stirring in the septic tank.

 

[Highbeam]

"In a septic tank the effluent with settle and the solids turn to sludge that slowly deteriates with bacteria and the "water" overflows to the leach bed."

This isn't quite right. The sludge sinks and the scum floats from the incoming sewage. The clear(er) zone in the middle is the stuff that leaves the tank after it's been in there a while. It leaves by being pushed up and out through the final baffle. Not overflowing. If you look into the typical tank you will see the lovely scum on top made of fats and greases, brownish whitish usually.

Pretty close though, maybe that's what you meant to say. It is important to note that there is an inlet baffle as well as an outlet baffle. The fresh sewage is introduced to the clear zone so as not to stir up the sludge or the scum. The inlet baffle is sufficient to dissapate the energy and prevent stirring. Oh and there is also that ridiculous center divider with baffles to pass fluid from the clear zone on one side to the clear zone of the other. The center divider only works to reduce the efficiency of the tank but is required un our state until the health departments wise up.

I suspect the maximum slope in the pipe is to prevent the fluids from rushing down the pipe faster than the solids. The solids would then stop floating, set on the pipe bottom, and then glue themselves to the pipe and cause pluggage.

2" gravity pipe is not big enough. Even a single home toilet is plumbed with 3 or 4" pipe. I would not recommend 2" gravity pipe for anything but connection of a grey water device to the sewer service mainline which is 4" or more.

 

[Dmace]

Highbeam, your desciption of the septic tank operation is right on. I got ahead of myself and skipped the whole baffle part /forums/images/graemlins/blush.gif. By overfilling, I meant over the seperator and then that compartment flows through the exit baffle and into the leach bed.

To furthur clarify, the 2" maximum pipe I was referring to was for a pump system, for gravity fed 2" is minimum. Obviously, the bigger the better but only up to about 4". As long as it's schedule 40 PVC.

 

[midlf]

We have a sewage line that runs the length of the house in the basement, long line, longer story. We had the plumbers replace it. They were extremely careful to pitch it at 1/4", exactly. They said too much pitch and the water leaves solids behind. Too little pitch and the solids settle out.

 

[Onthesauk]

We've got close to '100 foot inside the house, close to the 1/4 pitch mentioned, and all 4" pipe. Once it leave and house it makes a 90 degree turn and runs down at about a 30 degree angle for about '100 to a 3 chamber septic tank. From the pump chamber it runs '300 feet down hill at between 30 to 45 degrees to the drainfield. Designed and permitted for a four bedroom house with only two of us in the house and we seldom if ever use the garbage disposal. In use now for over 5 years with no problems.

 

[Marty NC]

First of all just joined I know this is an old thread yet it has very good extensive information on it. I do have another question that I can't find yet

I am talking from the septic tank to the Leitchfield is my question, not from the house to the septic tank but from the septic tank to the Leitchfield. Is there a maximum distance and or a maximum slope. Reason for my question is I would like the Leitchfield to be about a quarter mile from my house. Building a home in the mountains of North Carolina and there's really no level terrain anywhere. Where I would like the Leitchfield is the closest level terrain. Actually part of the thought was the septic tank itself would not be too far from the house meeting all the requirements everyone is talked about yet from the septic tank to the Leitchfield, that Line would be in the middle of the road I would be making up the mountain to the house. And the Leitchfield would be at a level train near one of the turns in the road.

Any feedback is definitely appreciated

 

[newbury]

I am talking from the septic tank to the Leitchfield is my question,

Any feedback is definitely appreciated

It's a leach field.

 

[Citydude]

The leach field doesn't have to be on level terrain. An engineer can design a field on a hill side.

 

[Marty NC]

OK can leach field be a quarter-mile from the septic tank?