Septic Experts -- Adding Septic after cabin is built

[PorkChopsMmm]

I started a build thread located here...http://countryplans.com/smf/index.php?topic=11644.msg149652#msg149652

Our cabin was designed from the get-go to be off-grid using a well and solar along with a composting toilet and grey water.It is on a post and pier foundation. After some use of our Biolet and preparations for moving to the cabin full-time my wife wants to get a septic tank installed. A lack of foresight on my part was not thinking of the layout of the cabin and where septic would go. Below is a MS Paint rendition of our cabin, its location, and where some land features are.

Important! We built this entire building without pulling permits. Running septic through the proper channels would require a building permit and a hook-up with the local power company. We don't want to go that route and my local excavator will put in whatever septic system we want without a permit. He has been doing it in the area for 40 years, but I want to know what you think is the best location.



- Cabin is 3 bedrooms 1 bath. Grey water for sinks and shower although we may run normal plumbing in the future.
- The well is ~35 feet from the toilet.
- The woods behind the cabin extend for another 800 feet or so.
- The open field in front of the cabin extends for 600 feet or so. We were hoping to either raised bed or in the ground farm some of this field.
- Ground is loamy sand after you get past ~6" or so of top soil and it drains very well.
- The well is a driven shallow point and it hit water about 15 feet down and the point is down to 25 feet.
- When digging down water can start to collect around 4 feet.

I have a few questions...
1) I have read different opinions on this... can we do a drainfield with this high of a water table? Our neighbor has one and he has very similar land characteristics.

2) We were hoping to either have raised beds or some farming in the field in the diagram. Would you have any concerns on doing raised beds above a drain field? What about using an area above a drain field for a fire pit, playground, etc?

3) Would some of the newer plastic drainfield pieces allow for occasionally being driven over? In the picture the driveway ends at the side of the cabin, but building out the garden, bringing out firewood, etc. may require transitioning from the driveway to the open field near the firepit, sandbox, etc.

I think we will need to put the drain field out in the field but I don't want to limit use of the field for farming if possible.

[Alan Gage]

Out in the field seems ideal. You could leave most of it untouched and still do whatever you want on it. I installed 200' of leach field using the 3' plastic vaults. I have 4 rows @ 50' long each. If I remember correctly the rows must be at least 9' on center apart, so I have 6' between rows. So the whole thing is 30' wide. 30x50 for the whole field.

Originally I thought about going with the old school leach field to save some money over buying the vaults but after asking around I found out all anyone uses around here anymore is the plastic vaults so that's what I ended up going with. I'm glad I did. They went in super fast and are supposed to work a lot better. And at least around here gravel is getting really expensive so I don't know how much cheaper it would be after you factor in the extra labor.

I heard from one installer that prefers to install the 2' vaults instead of the 3' ones because they can take more pressure if someone drives over them. That means more leach field though. I don't know how much weight they can handle.

I don't know what to say about your high water table. Does your installer have any insights? I'd think he should have a pretty good idea how it's done in the area. Either that or call up some of the suppliers of septic tanks and supplies, everyone I asked questions was more than happy to answer them.

Alan

[mpls_ham]

Not knowing the topography of the land makes it difficult to give advise.  Gravity is the key.  From your sketch I would put the tank in front of the driveway for easy access and run the drain field straight down towards the open field.  I would keep any car or truck off the drain field under any circumstances but a lawn mower or atv would be fine.  Installing all of this is sketchy without permits but if you never/ever plan to sell........Your best bet is to pick all of your neighbors minds and see what they have done.

[Alan Gage]

Oh yeah, you might check online to see if you can find the state regulations. Iowa has their listed online and it was a good source of information on what is and isn't approved. I realize you're going to fly under the radar but the regulations gave a few alternatives to the standard installation based on different soil types and water levels.

Alan

[Squirl]

1. Probably not.  In my jurisdiction that would surely fail.  They do a deep hole test at 6 ft.  If it fills with water it fails for a conventional septic.  The reason is they don't want someone's septic draining directly into the ground water in case someone has a shallow well.  People are generally cautious of this when there is a shallow well in the area.  Especially if the well is downhill.

2. Raised beds. No.  A leach field is to be as close to the surface as possible and just deep enough to make sure that no water can get to the surface.  Most states mandate a minimum depth.  The state I am in requires the pipe to be placed between is 2 inches minimum and 12 inches maximum depth.  Then the rest of the trench is below that. The important thing is plant uptake of the nitrogen.  The roots from a raised bed would not get down that deep, and the walkways around a raised bed would be devoid of plant life. 

3. Yes infiltrator pipes can be driven over.  It is important not to compact the soil around them or kill the grass.

[OlJarhead]

I'm curious:  do you live in the cabin now or is it just a vacation property?  Sunmar makes excellent composting toilets that work great.

[alex trent]

Given your "surface to water in the well" depth and your water 4 feet below the surface you have a real situation.

1.  You will have poor field drainage, which will make for septic field problems. A stinky field inhibits the country feel it seems like you built for.

2. You will need to need to be far, far away from yours or anybody else's shallow well for health concerns.

[rick91351]

I started a build thread located here...http://countryplans.com/smf/index.php?topic=11644.msg149652#msg149652

snip..............................................

I have a few questions...
1) I have read different opinions on this... can we do a drainfield with this high of a water table? Our neighbor has one and he has very similar land characteristics.

2) We were hoping to either have raised beds or some farming in the field in the diagram. Would you have any concerns on doing raised beds above a drain field? What about using an area above a drain field for a fire pit, playground, etc?

3) Would some of the newer plastic drainfield pieces allow for occasionally being driven over? In the picture the driveway ends at the side of the cabin, but building out the garden, bringing out firewood, etc. may require transitioning from the driveway to the open field near the firepit, sandbox, etc.

I think we will need to put the drain field out in the field but I don't want to limit use of the field for farming if possible.

I am not a licensed installer, I have put a number of systems in.  They have all been permitted and all above board.  I have found the local District Health Department here in Idaho great to work with.  However with that said looks like that is not in the cards so.......   

First just because the neighbor has similar land does not really mean anything.  It is what is under the land.  Our septic went in a good 500 ft from where we want to build.  It would not pass a perk test anywhere we wanted to build.  So we changed where we were going to build.  That was easy and now looking at it; it is a far better place to build.  Some people do not have that luxury.  By the way where we wanted to build is a dry sage bush covered field.  Three feet down it is like a lake.  We were never so surprised.  I mean it was instantly water rolling in.   

Second what are your concerns about raised beds?  In my opinion they would be very safe as would be fire pit and kids play grounds.  They are not no mans lands.  Most places you never know they are there.  Grow a lawn on top of them if you want.  We even irrigate over our drain field, as it is in our pasture.  Once a week, we flood irrigate the pasture.  I know that this is not recommenced but there is no health code or local code saying you can not.  Just do not drown the drain field, sprinkling would be much better.   

I am way, way more concerned about your high water table and shallow well versus septic tank and drain field leching into the well.  That is why there are minimums of distances, and everything should observed.  Drop into your local health department and ask them for your guide lines.  Or you can down load them off the internet in most states.  You do not have to submit to the thrid degree or anything you just want the minimums for septic systems.  It will show like 100 ft from a well, 100 ft from live water (a creek)  Here they can be right to the property line other place I have heard require a set back.  Sewer line have to be buried so many feet from the pipe bringing water in to your dwelling.  So on and so on.....  They are not hard to understand and are very sensible.

Third the Infiltrator chambers or "the newer plastic drainfield pieces." They are a good way to go as far as I am concerned.  I have put a number of them in.  However I would never drive over them.  Yet I do on occasion here in our valley property.  Our ranch never.  Here it is once in a great while and only when there is no other alternative in the pasture.  But as long as they have been in I would think there would be very little chance of damage.  As far as farming so long as you are not farming with those big huge honking  tractors and you are crossing at right angles.   I think you would be safe, as would grazing livestock.  However do not drive over them, once you do, you are opening Pandora's Box.  Well we did last week turns in to daily real quick.                   

[PorkChopsMmm]

Thank you for all of the replies and great info. You all are right -- I need to figure out how high the water table is. I have a feeling the field in the picture does not have as high of a water table as near the cabin -- some digging was done in the field and I didn't hit water. I know now to go back out there this Spring with a post hole digger and do some checking.

Here is some info from the application for septic from my county.


How far can you generally run plumbing to the septic tank? For example, if I wanted to put the septic tank 50 feet (minimally) from the well on the RIGHT side of the picture, this would make the run from the toilet to the septic tank ~85 feet or so. Is this possible?

Thanks again for the help!

[rick91351]

According to what you posted: How far can you generally run plumbing to the septic tank?  You posting shows 10 feet....  or am I missing something here?   

" I know now to go back out there this Spring with a post hole digger and do some checking."  You do not need a post hole digger but a backhoe one that will dig down at least 6 feet.........  Then is need to sit far at least 24 hours from what I remember.  Then you check if there is water in the hole not good.  This needs to be done in the area of the proposed septic tank.

As far as running waste just remember it all flows down hill.   
 

[Squirl]

It depends on slope/depth of tank/pipe size.

(a) House sewers are laid on firm foundation at a minimum grade of one-quarter inch per foot preferably without bends. At least one cleanout with a properly fitted plug is to be provided. The house sewer shall allow for venting of gases from the sewage system.

Other parts of the plumbing code state that it must be 4" pipe.  So at 85 ft a 21" drop.  Then you have to slope the trenches:

(v) In gravity distribution systems, the pipe shall be carefully sloped at between 1/16 inch and 1/32 inch per foot. Grades shall be determined by an engineer's level, transit or carpenter's level.

They have done many studies to come up with these slopes.  Too steep and the water runs faster than the solids.  To shallow and it doesn't have enough force to distribute.

I haven't checked the plumbing code to see if there is a maximum length to a house sewer line.

[PorkChopsMmm]

According to what you posted: How far can you generally run plumbing to the septic tank?  You posting shows 10 feet....  or am I missing something here?   

Sorry, I think my question was confusing. Can I have a toilet 85+ feet away from the septic tank? I have heard that you need a downward slope of 1/8" per foot, so that would be ~11 inches. I didn't know if there is some rule of them on how far away a main residence could be from the septic tank. In this scenario, the septic tank would be on the right hand side of the picture and 50 feet away from the well. Picture below.

This needs to be done in the area of the proposed septic tank.

Isn't it also important for the drainfield? I mean the septic tank shouldn't be seeping... but the drainfield should.

[PorkChopsMmm]

Thanks Squirl!

It depends on slope/depth of tank/pipe size.

(a) House sewers are laid on firm foundation at a minimum grade of one-quarter inch per foot preferably without bends. At least one cleanout with a properly fitted plug is to be provided. The house sewer shall allow for venting of gases from the sewage system.

Other parts of the plumbing code state that it must be 4" pipe.  So at 85 ft a 21" drop.  Then you have to slope the trenches:

I thought I read somewhere it is 1/4" inside the walls of the house and 1/8" outside the walls of the house. I will double check since than can make a difference.

I haven't checked the plumbing code to see if there is a maximum length to a house sewer line.

I will research this too. I always try to turn to others who know more than me. Thank you for the advice!

[alex trent]

There is considerable doubt about the max slope. Leaving solids behind in residential systems is not generally an issue. Kind of a tale that has taken root. A lot of local codes do not specify max slope, just min.  The max is often just a recco...so check that. A max of 1/8 inch does not make any sense as far as the laws of physics...or crap... are concerned.

My personal experience on 100 feet at 3/4 inch per foot. from toilet to sewer line in street is that in three years with low flush toilet not a problem. run the shower down that line and you flush good with the volume and the soap.

I have a 30 degree bend in the pipe about half way in. Note in the code that is cited, it says "preferably without bends".

If you cannot get by with this because of code, and cannot slope the line like code may want, you can always do a 45 degree drop from one level to the other and get the result with no "clog" risk.

[rick91351]

Gentle bends or think more as curves are what you want to do if you can not run straight.

As far as down hill, I have done drops with 90s and work very well.



There are two 90 degree 6 ft drops here down to the septic tank at least 150 feet away from our RV pads.  I think there is more of a rise here than it looks.  That is what the health inspector wanted, and that is what he got.  It has never in four year of pretty good us given us a bit of problem between the two RV pads.  The other pad sits at a 90 to that one, just to the right

The house will go about where I am standing and about forty feet from the septic tank.     

[PorkChopsMmm]

Thank you for all of the replies, guys. Here is a diagram describing where I think I could put the septic tank and drain field. This area for the drainfield would put it in a place where it will not get driven over, can be within a few inches of the surface, and I think have enough vertical distance to be away from the groundwater. It looks like the distance of the drain pipe from the house to the septic tank won't be a problem distance wise. Also, the drain pipe would be ~10 feet or so away from the well when it passes by... I could make wider if needed.

The downside is I will need to clear out some trees from this area... but I am thinking this would make a nice shooting range!

[rick91351]

Assuming north is the top of the map.  Just for reference.  Can you go south and put it in that green area?  Lot less excavation and also there it looks easier then you have to have your tank pumped.

Or is this in the the high water area?  I do not know how much hose they carry but there is a limit.  Also taking in to account Murphy's Law.  If there is an access to that area and you tank is backed up.  It will not be accessible because the rain, snow, lack of easement, how just fill in the blank_________.  With that call RotoRooter or a pumping service and and ask them how much hose do you carry for a standard pumping fee.  That said they can bring out more hose.  However here that would be another service call.  I would think you would not want another service call and fee for that.  Remember what is agreed on today, five years from now is out the window.   

Also remember most peoples tanks are in their front yard or back yard.  Like I say it is not a no mans-land.  I would try and position it to bottom or south of the map.   The outlet is fluid only, no solids allowed!  So it can turn at a 90 or forty five.  I think they want a 10' straight piece minimum.  But where this is non-permitted you can do anything you want.  But try to remember minimums are there for a reason.

Next on the addenda..... How are you going to run you vent pipe in with this new fangled flusher?             

[mgramann]

I'm coming a bit late to this discussion, but would a "mound system" help with the high water table?

[firefox]

Just curious, is it possible to put in a permanent hose sustitute going from the tank over
to the road access? This way a pumper can come to the end of that and hook up without
the extra hose requirement.
Bruce

[PorkChopsMmm]

Assuming north is the top of the map.  Just for reference.  Can you go south and put it in that green area?  Lot less excavation and also there it looks easier then you have to have your tank pumped.

Or is this in the the high water area?  I do not know how much hose they carry but there is a limit.  Also taking in to account Murphy's Law.  If there is an access to that area and you tank is backed up.  It will not be accessible because the rain, snow, lack of easement, how just fill in the blank_________.  With that call RotoRooter or a pumping service and and ask them how much hose do you carry for a standard pumping fee.  That said they can bring out more hose.  However here that would be another service call.  I would think you would not want another service call and fee for that.  Remember what is agreed on today, five years from now is out the window.   

Also remember most peoples tanks are in their front yard or back yard.  Like I say it is not a no mans-land.  I would try and position it to bottom or south of the map.   The outlet is fluid only, no solids allowed!  So it can turn at a 90 or forty five.  I think they want a 10' straight piece minimum.  But where this is non-permitted you can do anything you want.  But try to remember minimums are there for a reason.

Next on the addenda..... How are you going to run you vent pipe in with this new fangled flusher?           

Rick, all great info, suggestions, and questions. Actually, the map is upside down. In the picture South is "up" and North is "down". If I go South (or up) in the picture, beyond where our expansion plans are, then we would need to knock down even more trees. It is possible, but I haven't even staked out where the addition will be or know how we want to build it. Maybe I need to put on my big boy pants and just make a judgement call.

My plans for the vent pipe were to run one alongside the house going up to the roof. Bad idea?

[PorkChopsMmm]

I'm coming a bit late to this discussion, but would a "mound system" help with the high water table?

We are off-grid and unless we had gravity working for us, e.g. a hill or some such, we would need to us an electrical pump to pump the sewage "up" to the mound. We don't have any hills or elevation changes like that.

[PorkChopsMmm]

Just curious, is it possible to put in a permanent hose sustitute going from the tank over
to the road access? This way a pumper can come to the end of that and hook up without
the extra hose requirement.
Bruce

Thanks Bruce, didn't think of that!