My building has septic tank on its southeast corner.

I have no manhole cover, i.e, upward/eastward/westward/northward access to my septic tank, it's all covered.

I can access it through south wall only. So both input and output (200 mm capped pipe to allow tankers to suck the septic) is on the same side which is south.

I'm trying to make a hole in the south wall, (it's the only way) and take the filtered water to percolation tank so that water can be drained easily and I don't have to pay for septic tanker lorry once in two months.

enter image description here

To take the filtered septic water we can use baffle filter but it's quite vertical in and it would have to be placed inside septic tank and sealed with cement from south side wall.

But after sometime if baffle filter gets clogged, I will have to get rid of the cement coverings from the south wall and take out the filter and clean and keep it inside again.

enter image description here

I'm wondering if I could have some kind of standard inline filter which is outside of the building south wall. It would then be easy for me to clean in case if it gets clogged.

Can someone recommend me a wise idea to deal with my circumstance?

Can I place vertical baffle filter horizontally to the pipe outside of the south wall? Would it work properly?

Update 1:

I mean to say there is a room on the north wall so I can't break the floor and break the north wall of septic tank. Beyond east wall I don't have any land left , on the west there is another room .. so I can't take drain pipe from septic tank there as well. South wall is road facing side so I can take drain pipe from there only. Besides the septic tank inlet is also on the south wall, Ideally I should be having 2 brick walls from south to north inside septic tank so the water than arrives in Northen most chamber will be free from scum or sludge and I should be taking water from here to cess pit. But my septic tank has only one chamber. I want to have a filter outside the south wall which is effective and I should be able to clean the filter once in 6 months.

Update 2:

Here is an excerpt from Government code for areas where there's no Sewage Treatment Plant or Public Sewage line is not there.

A septic tank system is a typical on-site treatment facility that consists of a septic tank and a soak pit and employs two technologies: the first is anaerobic treatment and the second is the methods of letting treated sewage penetrate the ground. It shows stable performance, provided that the water temperature is kept suitable to digestion and the soil has good permeability. Part A: Engineering 9 - 2 CHAPTER 9: ON-SITE SANITATION However, the septic tank reduces BOD up to 50%, so if underground penetration is impossible due to high groundwater levels, rocky strata, non-availability of land for soak-pit, another method must be employed to hygienically treat sewage passing through the septic tank such as anaerobic filter and contact aeration. When this system is applied to an urban area with high population density, care must be taken not to have a negative effect on the surrounding environment.

  • If you have to get it pumped every 2 months then you either have a completely failed drain field, or what you have is not really a septic tank, but more of a holding tank. Is the photo in your question yours, or is it just something you just pulled off the web?
    – brhans
    Commented Nov 17, 2022 at 1:23
  • not sure what the north - south have to do with anything.
    – Traveler
    Commented Nov 17, 2022 at 3:37
  • @brhans - It's something I took from web to give an idea about how usual baffle filter looks like in septic tank
    – Amogam
    Commented Nov 17, 2022 at 7:43
  • @Ruskes - Please find the update
    – Amogam
    Commented Nov 17, 2022 at 7:53
  • are you planing a single stage or multiple stage filter
    – Traveler
    Commented Nov 17, 2022 at 8:31

1 Answer 1


You have to design a multi step system which will address so many factors like Air pressure , Pathogen , Scum , Sludge , Water overflow, odour , mosquitoes, leach, insects , keeping the bio activity alive in septic tank etc..

First Step: Membrane filter

I can give you a rough idea Just build a concrete cube with Baffle filter standing vertically in it and keep a air tight concrete slab on top of it.

Connect a pipe directly from your septic tank to the cube

  • Have a RO(Reverse Osmosis) membrane on the pipe which is on cube side. So you can change the membrane once in a year and the water that comes to the cube in mostly clean and free of bacteria.

  • Have a Super sponge next the RO filter , this helps too

  • Have a metal filter as well

Have all this one after another.

Purpose: Remove pathogens and solids

Second filter: Baffle filter

Install a Baffle filter and keep it upright in the centre of the cube and connect the lower end of filter to the pipe which leads to cess pit.


If RO membrane fails then this can atleast keep the solids away from entering into cesspit.

If possible have a Geofabric filter of 5 GSM on top of this RO membrane with some gape in it.

if solid enters into cesspit then over the time. Cess pit will fail as well.

Third Step: Disinfectant dripper

  • Have a dripper attached to each cesspit serially and have the liquid coming from a small liquid storage.
  • Pour a baking soda mixed water first week of the month and let it drip away the whole month.
  • Pour boric acid mixed water second week of the month and let it drip away the next month.
  • Pour Chlorine mixed water third week of the month and let it drip away the next month.

Purpose: To kill the pathogens and keep rats, cockroaches , termite ants,mosquito larva, mosquito away.


The water should not go back to septic tank from Cesspit or else the biological digesting system inside will die

Fourth Step: Mushroom air vent(Charcoal) & Drain pipe vent

  • Have a mushroom air vent and load charcoal into that so odour is kept away.

  • Have a drain pipe through which you can pump the water out if required.

Purpose: To keep the odour away and pump the water when required

Fifth Step:Increase Bio Activity

  • Make sure you never use acid on cleaning WC
  • Drop inoculum bacterial culture liquid into your WC once in 6 months.

Sixth step: Water tight cess pit

  • Cess pit should be sealed completely with concrete on top and sides , so rain water can't get and if water level increases during the rainy season you can prevent the water from leaking above the ground.


Take all this with pinch of a salt.Good luck


  • Cesspits should be kept on the side where tankers can access it easily.

  • The greatest risks of pathogen exposure to human and cause subsequent illness comes from below

    • Being unprotected when Emptying out the cesspit
    • Through contamination of ground water and use the ground water from near by areas
    • When a cesspit is overflowing due to plumbing system malfunction or infiltration of rain water into cesspit

Reference[Global Water Pathogen Project]

Best thing to do is kill pathogens in cesspit with drip method I mentioned above


Like you said RO Membrane and other sponge filter will need more maintenance so

Please find my below sketch , it'll be low maintenance

enter image description here

Chamber 1:

It'll stop most of the sediments and scums.

Chamber 2:

Buy a good Effluent filter ,it's bit expensive but it's definitely worth it or else your percolation tank's bottom will get sealed with sludge over the time.

enter image description here

Chamber 3:

Fill this chamber with charcoals and also have inlet dripping pipe for chlorinating the water.

Don't forget to have a inlet dripping pipe for each percolation tank as well.

This will disinfect and finish off the alagaes.


Make sure 3 chamber's outlet is lower than it's inlet by 6 inches or 1 feet. so there's no issue of water backing up and killing off the bio culture in your actual septic tank or don't do the chlorination in 3rd chamber just do it individually in all 4 cess pits

Update: DIY Effluent filter

  • Buy a Stainless Steel 316 ( marine grade ) Mesh and make it like a sock.

enter image description here

  • Buy a non organic cloth and seal the bottom of the sock

enter image description here

  • Similarly make a collar on the top of the sock with non-organic fabric

  • Get a small handle made of SS 316 and sew it with the collar and top of the mesh

Make sure the T's height is 1 or half feet and SS 316 sock's height is 2 or 3 feet so the filter sticks out

enter image description here

so you don't have to clean the fillet for at-least 2 years.

enter image description here


Make sure the micron of SS 316 mesh is 1600 to 2000. So you won't have to clean the filter often and this is the standard size in domestic effluent filters( EF-4)

Reference for DIY Filter

Update 2:

Two more ways to handle the solid

  • Biological underflow drain ( In cess pit)

    • Just connect underflow pipes to all the cesspits
    • Fill the cesspits with bio coated material so when water comes up , bio matter grows and that keeps the water clean

The only problem is it can get clogged and cause overflow if not maintained properly

  • Upflow anaerobic filter ( Before cess pit )

    • It involves an chamber that's air tight.

    • Basically the first chamber and second chamber should be connected at bottom

    • Second chamber should have a filter medium completely from bottom to top and there should be a outlet pipe above the filter medium , basically this filters all the solids both settleable and unsettable and as the water goes slowly in the airless chamber the bio matter also gets digested by bacteria.

    • If you could use chlorinator on the water that comes out of this chamber then that should be it.

Reference 1 2

Update 3: Sand filter ( Gravity)

You could probably use slow sand filter. So like in the above update up flow chamber , you may use sand filter chamber

  • Have a slotted pipe at the bottom of the chamber

  • Quarter of the chamber has to be filled with gravel ( Coarse at the bottom and fine gravel at the top)

  • In the remaining space , fill exactly half of it with sand( Coarse sand just above the gravel and finer to the top )

So when the water comes , to this chamber .. the filter medium ( Sand ) filters solids, pathogens and let the water infiltrate to the support medium which is nothing but our gravel then through gravel water passes into the slots of pipe and that's our filtered outlet.

Downsides of Filter: You will have to clean it once in a while to keep it working ( I mean once in 3 months usually)

Best filter medium:

  • Sand
  • Activated charcoal
  • Cinder
  • Slag


You could buy chlorine tablets and drop into the cess pit directly through air vent.

  • 1
    Thanks for the detailed answer , it has given me some ideas. But my doubt is if chlorine is dropped into cesspit like you mentioned above... if water backs up to septic tank won't it kill the Biological system in septic tank ?
    – Amogam
    Commented Nov 18, 2022 at 17:49
  • Other than this the filters like RO membrane , Super Sponge .. will get blocked with dirt.
    – Amogam
    Commented Nov 20, 2022 at 9:26
  • Gravity filter is the sustainable long standing filter , so make use of gravity in the Chambers
    – CuriousMan
    Commented Nov 20, 2022 at 19:59
  • Thanks for the detailed answer. How do I add chlorine ? Manually ? or How frequently ? I am looking for a maintenance less approach ?
    – Amogam
    Commented Nov 20, 2022 at 20:59
  • Not sure about how much chlorine should be mixed as well ?
    – Amogam
    Commented Nov 20, 2022 at 20:59

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