Septic tank, D Box and percolation

yop

Folks,
Have a figure 8 tank, we are in a 4 bed house and in it since 2005.
No issue with tank until last Summer and one of the outlets began to bubble.
What has happened since is that I had the tank emptied last Sept and now its full again, of water mainly and then over the last number of weeks we have had water over the tank, up to an inch, this was mainly during times of use of the washing machine and/or shower.
Last year I also built a shed, this would be on the house side of the tank and also its in line with one of the outlets. Shed footprint is about 30*20ft.

So today I decided to get the shovel out and find the distribution box. It was circa 16" below the ground level and around 8/10 inches below the level of the tank.
It is connected to the tank with an angle coming out of the tank and then a pipe circa 4ft down towards the percolation. The percolation area is on a slope.

The Dbox has 5 outlets. Out of these outlets 4 of them are been used. 1 is going along the slope towards the direction of the shed.
The 2nd one on that side is capped.
There are 2 then on the opposite side and these are both used.
Then directly opposite to the inlet there is one, this is the outlet where the bubbling is occurring.

When I go down to the Dbox lid it had about a inch of water and when I got the lid off I spent the guts of 20 mins bucketing out water to get down to see the pipes.

What I notices is that:
a) the Dbox isn't level
b) on the outlet goin around in front of the shed, water poured back into the Dbox, instead of the other way!!!!
c) the level of the water going out of all pipes was not the same
d) each outlet has a 4" sewer pipe coming out it, to the outside of the tank BUT that outlet then has a 3" perforated drainage pipes coming from that, this is the pipe been used to the percolation area.
e) Had a lot of gunge and muck, not sewage if you get me

So what I am looking for is someone who can tell me what maybe wrong there.
From what I have read
The dbox needs to be level.
The 3" pipe isn't right


But does anyone have a doc which will give me a full spec of how this should be created and how it works even

Thanks

muffler

From what I can make out of that it appears that you have issues with levels and the percolation area in general. The piping in the PA should not be land drainage piping and should be 100 mm - 110mm dia. The PA also needs to be near enough level with a minimum fall only.

I cant find the old SR6:1991 manual on the NSAI web site but I did find it here (no connection with this crowd obviously). That may have been the standards applicable depending on what was contained in the Councils Development Plan at the time you sought and received planning permission but I linked to it as it gives a simple overview of septic tank and percolation area construction.

It would however be most likely that details of the waste water treatment would have been based on the requirements of the EPA manual - waste water treatment systems for single houses - see page 19 of the document and the pages following.

I would recommend that you get a site assessor to check all this before Hogans heroes arrive

yop

Cheers Muffler.
Only spotted that on the net about rigid pipes.
What do you make of them using 4" rigid then the flexi 3" just pushed into that, wouldn't make a great flow?
Would you think that I need to rip out the 3" totally?

Stone Deaf 4evr

yop wrote: »

Cheers Muffler.
Only spotted that on the net about rigid pipes.
What do you make of them using 4" rigid then the flexi 3" just pushed into that, wouldn't make a great flow?
Would you think that I need to rip out the 3" totally?

Distibution box should be level so the water doesn't favour any particular exit pipe. Depending on the type of percolation area you have, there may be an issue there. For example, if the tank had overfilled with solids before you emptied it, it may be that some solids have made their way out to the dist box, and on to the perc area. If one pipe run is favoured, its possible that some of the holes have now blocked up and aren't leaving the water escape.


However - even if one pipe which was favoured was to block, the water should rise in the dist box to escape out of one of the other outlets.


Sorry if its not a definite answer, points worth thinking about.

yop

Stone Deaf 4evr wrote: »

Distibution box should be level so the water doesn't favour any particular exit pipe. Depending on the type of percolation area you have, there may be an issue there. For example, if the tank had overfilled with solids before you emptied it, it may be that some solids have made their way out to the dist box, and on to the perc area. If one pipe run is favoured, its possible that some of the holes have now blocked up and aren't leaving the water escape.


However - even if one pipe which was favoured was to block, the water should rise in the dist box to escape out of one of the other outlets.


Sorry if its not a definite answer, points worth thinking about.

Hi, thanks for the reply.
I get what you are saying re the others taking the flow, doesn't seem to be happening. I am really wondering if that 3" pipe is fecked in the ground!

muffler

Nothing wrong with the 4" solid piping provided its perforated or laid un-jointed as specified in the manuals. I would be concerned at the method of basically sticking one pipe inside the other as that junction can result in possible obstructions.

As you are probably aware land drainage pipes are perforated right around the circumference and are meant to take water in. So by using this type of pipe you are effectively drawing surface/rain water into the percolation area and thereby preventing the waste water from the septic tank being effectively distributed throughout the pipes and percolated naturally into the ground.

In saying all that I have seen the land drainage pipes being used and they would have worked to a degree but that would have been in soil with certain characteristics - basically good dry ground to keep it simple.

I suspect that your entire system needs to be checked i.e tank and percolation area an as stated I would advise getting a good site assessor out to assist.

Stone Deaf 4evr

Just a bit of clarification - when you say 4 inch pipe out of the dist box to 3 inch, I'm assuming this is a ready made box, not a manhole that's been built to suit? As in its a solid plastic unit that has moulded 4" holes on it for connecting pipes?

If so, how are the 3" pipes connected? Is there a joiner of some sort.


You also mentioned that water flowed back into the box from the shed side - are you sure its a backfall, as opposed to the water simply not being able to flow out of a fully filled pipe, so when the level in the dist box drops, it simply finds its level by flowing back into the pipe.


Btw, I'm a civil engineer and I've overseen many installations of these. If you want me have a chat over the phone I could pm you my number tomorrow rather than typing all this out on the phone!

Stone Deaf 4evr

muffler wrote: »

Nothing wrong with the 4" solid piping provided its perforated or laid un-jointed as specified in the manuals. I would be concerned at the method of basically sticking one pipe inside the other as that junction can result in possible obstructions.

As you are probably aware land drainage pipes are perforated right around the circumference and are meant to take water in. So by using this type of pipe you are effectively drawing surface/rain water into the percolation area and thereby preventing the waste water from the septic tank being effectively distributed throughout the pipes and percolated naturally into the ground.

In saying all that I have seen the land drainage pipes being used and they would have worked to a degree but that would have been in soil with certain characteristics - basically good dry ground to keep it simple.

I suspect that your entire system needs to be checked i.e tank and percolation area an as stated I would advise getting a good site assessor out to assist.

The land drain should work fine, the problem with it is that if any solids make their way out, the corrugated internal surface of the pipes tends to grab this muck. I don't think you'll draw water into the percolation area as such, this depends entirely on the area though, I.e. is it individual trenches or built up as a bed.

muffler

Stone Deaf 4evr wrote: »

The land drain should work fine, the problem with it is that if any solids make their way out, the corrugated internal surface of the pipes tends to grab this muck. I don't think you'll draw water into the percolation area as such, this depends entirely on the area though, I.e. is it individual trenches or built up as a bed.

In my experience the land drainage piping will only work in rare occasions as I mentioned earlier. In any event the internal walling of the pipe should be smooth to avoid solid matters catching & solidifying, even simple matters such as toilet tissue.

tred

IT might be also worth inspecting the percolation area, if it followed spec, and they just didnt throw daub under it, which could now be hardening.
Wavin do specefic percolation pipes with little holes at the bottom. I wonder is it worth inspecting the percolation mini camera wise, before ya start digging. If you only having issues with one pipe..could you temp block it..see how everything behaves...??..block it at the distribution....

mickdw

Timewise, is there any connection between shed building and problem starting?

yop

Sorry lads never got the update emails on this.

Shed was built after the issue arose, BUT it has gotten worse. I do believe that its added to the issue. To rectify that I will be running the rainwater from the shed to a new location in its own soakpit so to speak.

Since Saturday I had a check with an engineer, but previous to that I have made the decision to redo the full system.
Percolation pipes are down with 3" land drainage and I can only rod up to 4ft into them, so they are not doing their job and are too far below the surface, this occurred after we had to raise all the ground.

So I am also going to raise the septic tank to the level of the land around it as oppossed to it been lower, due to the rising of the land again.

The Dbox is to be taken out and redone. I will be using perforated 4" sewage pipe now on all outlets and in the percolation. Also will be putting a membrane above to stop any potential soil seeping down onto and blocking the pipes in the future.

I will be literally up to my arse in sh1iididite

Stone Deaf 4evr

yop wrote: »

Sorry lads never got the update emails on this.

Shed was built after the issue arose, BUT it has gotten worse. I do believe that its added to the issue. To rectify that I will be running the rainwater from the shed to a new location in its own soakpit so to speak.

Since Saturday I had a check with an engineer, but previous to that I have made the decision to redo the full system.
Percolation pipes are down with 3" land drainage and I can only rod up to 4ft into them, so they are not doing their job and are too far below the surface, this occurred after we had to raise all the ground.

So I am also going to raise the septic tank to the level of the land around it as oppossed to it been lower, due to the rising of the land again.

The Dbox is to be taken out and redone. I will be using perforated 4" sewage pipe now on all outlets and in the percolation. Also will be putting a membrane above to stop any potential soil seeping down onto and blocking the pipes in the future.

I will be literally up to my arse in sh1iididite

Couple of things here.

1. if the rainwater from your shed was being dumped into your foul system, overloading can easily become a problem.
2. If you can only rod 4' into them they are either after getting blocked or crushed - possibly when building the shed.
3. Raising the septic tank and renewing the percolation are will definitely solve your problem but it seems like overkill - when planning permission was applied for, a percolation test would have been done on the ground at the level the percolation area was to be installed at that would have specified the amount of piping that was needed and whether or not imported material such as drainage stone was to be used. I would be of the opinion that you should be able to renew your area only and avoid raising the tank. I would also at that time run a land drain around your percolation area to prevent any surface water from entering the system - this will combat the overloading.
4. is it possible to raise your tank level without changing the levels of the pipes coming out from your house, and maintaining the correct slope for self cleaning?