Septic System Standard Rock Leach Field

glenn kangiser · January 14, 2006, 11:11:25 PM

As I was finishing a septic system the other day I thought it might be a good idea to snap a few pictures and post them here.

The official from the health department first came out to the site and had us dig profile holes. Upon inspecting the soil for acceptable qualities he wrote up a system design based on the number of bedrooms in the proposed house, distance to the well and seasonal water runoff. Note that it was necessary to build a burm around this leach field and provide drainage around it so stormwater runoff from the adjacent hill would not flood it and saturate the field causing the system to stop working. This was not yet requested by the official but upon seeing the problem I remedied it before he required it. A good rain tried to flood it during construction. Note that work cannot be done during excess water conditions or it will be rejected due to sealing of the soil causing lack of flow.

Size is based on number bedrooms x appx 375 square feet of side surface area per bedroom. Both sides of each field line are counted so two lines 100 feet long are required for a 3 bedroom house. Lines are limited to 100 feet maximum and are level to 1 or 2 inches of slope overall per the inspector.

In our case he specified 3'6" depth with 30" rock under the pipe and 2" over it -4" SDR 35 pipe so a total of 36" of 1 1/2" nominal size rounded rock.

The contour of the land must be followed so we determined the lay of the fields with a laser. The laser was also used to check the bottom of the trenches, top of the rock fill and top of the pipe on the rock. We put the rock in in piles and leveled the top in order to continue working while we waited for more rock to arrive. Usually 40 to 50 cu. yds. of rock are required.

A concrete or plastic distribution box is set in wet concrete and leveled while on the concrete to make sure that an equal amount of effluent goes through each pipe to the drain field. The inspector prefers that water is used as a level in the box to be sure it is correctly leveled. If flow is not even it is rejected. A minimum of 5 feet of solid pipe is required between the "D" box and the perforated pipe to prevent settling of the box.

By using a distribution box multiple lines on different elevations can be used, each getting the same amount of effluent. Our second line was about 10" lower than the first one due to the slope of the land.

The completed installation is then covered with straw to act as a filter material allowing moisture to move up but impeding the flow of topsoil into the rock of the leach field.

Normally I would leave the straw exposed at this point for the inspector to check the lines, but the owner here has cows who do not seem to know that straw has no food value, so if it is left exposed they will trample through the leach field and eat it. :-/

bayview · April 07, 2009, 07:25:55 AM

Thanks for the pictures . . . Very informative.

You have a total leach field of about 200 feet. (?) If you didn't have a deep lot could you have gone with 4 lines of 50 feet each?

What other limitations have you experienced?

We have been informed that we can only use an aerobic system since we are on less than ten acres. . . (Texas) Many standard systems are being installed by do-it-yourselfers illegally.

April 07, 2009, 07:38:16 AM

Here in Oklahoma you must be licenced to install a septic and you can't get water without it. Despite 30 years of plumbing experience I had to hire a contractor to do mine.

Nice work on the septic glenn even if this thread was necroed.

pagan · April 07, 2009, 08:20:58 AM

Glenn,

Ever do anything like the Watson Wick?

bayview · April 07, 2009, 12:38:52 PM

ScottA:

What type of system are you required to install?

April 07, 2009, 01:58:53 PM

How large is the septic tank ?

how far is the tank from the distribution box ?

I think I will copy this at the farm.

Thank you very much

ScottA · April 07, 2009, 04:03:32 PM

QuoteScottA:

What type of system are you required to install?

The same as the one in this thread. 1000 gal. tank and 200' of lateral lines in rock.

glenn kangiser · April 07, 2009, 05:36:12 PM

Quote from: bayviewps on April 07, 2009, 07:25:55 AM

   Thanks for the pictures . . . Very informative.

   You have a total leach field of about 200 feet. (?) If you didn't have a deep lot could you have gone with 4 lines of 50 feet each?

   What other limitations have you experienced?

   We have been informed that we can only use an aerobic system since we are on less than ten acres. . . (Texas) Many standard systems are being installed by do-it-yourselfers illegally.

Yes 200. I think we may have gone with a 1500 gallon tank. Cost difference is minimal.

I don't see any reason 4 shorter lines couldn't have been used - they just said not longer.

Even though there are lots of acres there, the place the lady wanted the house was limited by a seasonal stream just past the leach field, and I had to remind the inspector he was the one who gave me clearances to the seasonal stream as he mentioned a larger distance later and it would not have fit.

I am a general and well drilling contractor and since I had enough experience he let me do many of them up here. They really want a general engineering contractor here as I recall.

glenn kangiser · April 07, 2009, 05:39:59 PM

Quote from: ScottA on April 07, 2009, 07:38:16 AM
Here in Oklahoma you must be licenced to install a septic and you can't get water without it. Despite 30 years of plumbing experience I had to hire a contractor to do mine.

Nice work on the septic glenn even if this thread was necroed.

Thanks Scott. I have passed all of my inspections on my installations and our inspector is pretty good to work with.

April 07, 2009, 05:42:17 PM

Quote from: pagancelt on April 07, 2009, 08:20:58 AM
Glenn,

Ever do anything like the Watson Wick?

I haven't done the Watson Wick. Just standard rock and infiltrator modules.

glenn kangiser · April 07, 2009, 05:47:22 PM

Quote from: Windpower on April 07, 2009, 01:58:53 PM
How large is the septic tank ?

how far is the tank from the distribution box ?

I think I will copy this at the farm.

Thank you very much

I generally go with a bigger tank - generally 1200 to 1500 gallons if cost difference is not major and it is as large or larger than specified by the health department official.

Tank to D box in this case was around 50 feet to get past the driveway area and to a horizontally level area that was long enough for the fields. As I recall it is minimum 5 feet from the septic tank and 5 feet from the D box to the fields with un-perforated pipe the keep the D box from settling. The heath official wants the D box set in concrete - fluid enough to level it so that both or all fields receive the exact same amount of flow from the D box to each field.

Alasdair · April 07, 2009, 08:40:10 PM

Our situation in Nova Scotia is the same as Scott's - Must have an engineered system and a ticketed installation contractor to install any septic system - this will set you back $15000 CND in normal circumstances.
Before we bought our land (which fortunately already had a system installed) I decided that $15000 was a bit steep and looked into the certification - it wasn't the cost or time of the qualification that put me off but the two year "apprenticeship" that changed my mind ...

phalynx · April 20, 2009, 02:01:47 PM

Glenn or anyone, do you have any experience with the infiltrator plastic shells for septic? I have heard they are super easy to install and have a small footprint.

http://www.infiltratorsystems.com/

NM_Shooter · April 20, 2009, 07:24:12 PM

Wow... I thought that 2 lines 100' long was quite a bit. I don't think they size them to that extreme here.... dunno for sure.

It looks to be fairly shallow. Is the septic tank significantly uphill from the field?