Septic Tank Location

[longball53098]

I just finished reading hundreds of posts related to septic systems here in LOS and I did not see this info.

I am getting ready to build and I would prefer locating the septic tank away from the house closer to a wall. This distance would be in the range of 8 meters or so rather than right up next to the house within a meter or two. Is there a preferred distance ? I will be feeding this one tank from two toilets that are back to back in separate bathrooms. I want to use one common 4 inch pipe to the tank from both toilets. I seem to recall somewhere there is a best way to do this? To avoid some issues with one toilet sucking the water from the trap of the other? A proper soil stack maybe?

But the main question is about the tank and where it should be located Even farther is better for me if that's not a problem for proper drainage. I would think the only issue is the correct slope of the 4 inch drain line to the tank I may as well tack on another question here----------how far can the leech field be away from the tank outlet

Thanks in advance for the help

:D

[Rimmer]

Septic tanks should be placed 30m from any wells, 15 m from streams and 3 m from buildings and property lines.

Can't help you on the placement of a leeching field, seems this is optional.

A central air vent will (soil stack) ventilate the system and stop it sucking air when a toilet is flushed, it should be higher than the roof line to avoid smells. You can also put a check valve in the line if a portion of the pipe is over ground.

Use check valves on your gray water pipes if they join into the sewer pipe this will stop any slugs of water clearing out the U traps in the gray water system.

[Beardog]

Longball,

Your leech field should be 1 meter deep X 46 cm (18"-24" deep) X 7 meters long. This is standard in US. Europe & Australia.

It does not matter if it is 2 or 3 parallel trenches or if it is square going around the tank . I have also heard of people in Thailand running the drainage field deep & less are = the same measurements. the ground should be somewhat porous so the excess water will adequately drain away.It has to be 30 meters from your well so you do not contaminate your water source. the 4" pipes need a 40-1 slope. I put a y at the end of septic tank for easy access if it ever needs to be snaked. When puting in your 4" pipes make sure the lines are supported solid soil (no gaps) you can use gravel if you get dips in the trench. Put the 4" with a straight shot to the septic No 45's or 90's & don't forget your U trap from the gray water system if . I was able to run the exact

1 meter deep x 22" X 7 meters. This same design is used on the 4 houses around the corner. Flawless. We built the same system (except a heck of a lot larger in Portland Oregon (64 people ) & Loveland Colorado for over 300 in that commune in the 70's. http://www.thaivisa.com/forum/Septic-Tank-t168433.html this is the link to the forum topic Septic tank fills to quickly. Page 7 some diagrams on how the septic systems are built in our neighborhood. I consulted with one of our neighbors from england( we are both licensed plumbers) & the only variation I used was on the dam_n on the flow pipes( which can be made of any type of material that will not rot away. I used roof tile as it was cheap & easy & should last 10-15 years . We used a transit to shoot the slope to get the 40-1 ratio (I have heard of less conservative slopes used but why take a chance. I think Crossy had a design he posted around the same time with his diagram of the ditch going straight down for the drainage field. Do yoourself a big favor in case you decide to get some excersize -do not dig the drainage field yourself. It is a super pain in the ass. And the labor to dig it is inexpensive or 5500 baht or so for the excavator. if you go that route. Edit I forgot to mention the system is identical if you use cement rings or the standard DOS tanks premade. You might have a slight advantage with the cement rings as it holds 1/3 more substance. If you use the cement rings seal the bottom with cement to insure the best results.

PM me if you need some more help.

Edited August 4, 2008 by Beardog

[Naam]

Septic tanks should be placed 30m from any wells, 15 m from streams and 3 m from buildings and property lines.

Can't help you on the placement of a leeching field, seems this is optional.

A central air vent will (soil stack) ventilate the system and stop it sucking air when a toilet is flushed, it should be higher than the roof line to avoid smells. You can also put a check valve in the line if a portion of the pipe is over ground.

Use check valves on your gray water pipes if they join into the sewer pipe this will stop any slugs of water clearing out the U traps in the gray water system.

the air vent of the septic tank is meant to release pressure when toilets are flushed but will not necessarily prevent that flushing toilet "1" will not suck water from the U-trap of toilet "2" especially as the OP wants to use a single pipe only. thai toilets -unlike those in the U.S. and Europe- are quite often built without individual vents. if this is the case a separate pipe for each toilet should be used. PVC is dàmn cheap in Thailand.

as far as distances are concerned there is no limit AS LONG AS THERE IS ENOUGH SLOPE

[Yorkie]

as far as distances are concerned there is no limit AS LONG AS THERE IS ENOUGH SLOPE

As far as I remember the 'rule of thumb' gradient to give self cleaning velocity is:

2" dia. pipe - 1 in 20

4" dia. pipe - 1 in 40

6" dia. pipe - 1 in 60

etc.

Cheers

Y

[longball53098]

Rimmer, Beardog, Naam and Yorkie,

Many thanks for the input and fine information. I knew there were a few crapper drainage experts in the crowd.

I am nowhere near the hole digging yet but it's not too early to make the plan on placement of the components.

Again many thanks