Septic tank question

funnyname

Hi

Bought a house about 2 years ago, it was originally built in 2001. Seems to be a standard septic tank but it is covered by wooden shield but this is now beginning to rot. I want to remove this and rather than putting another timber cover on it I want to fill it in with earth but making sure that nothing is covered and not accessible.

I also had a look at the main manhole covers and one seems to be pretty blocked so I guess I need to get it de-sludged, I presume this full one is the main access points.

Am I right in thinking that I can fill it in as long as I leave the ventilation pipes uncovered?


See photos for set-up.



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Regards

FN

my3cents

Doesn't really look like a septic tank at all? A septic tank is a "tank" it has a base four walls and a top. Normally there is a baffle across the middle of the tank to ensure there is no direct flow from the waste in to the output to the percolation area. What I can see from your pictures looks more like some form of soakaway or filter bed.

Nekarsulm

Looks like your tank is already covered with earth and stone etc. Was the original builder planning to put a shed over it? That looks more like a shed base/floor then a cover.
there should be a galvanised steel man hole cover there somewhere, about 18 inches square, to allow inspection or (if required) sucking out with a vacuum tanker.

my3cents

There's no sign that the timber work was ever the floor of a shed or even ever intended to be, why leave the gaps between the boards. Looks more like it was put down to look like decking or just a cover to keep people from falling into whatever lies below.

Needs removing and clearing off by hand so you can actually work out what is going on. From the level of the pipes under the covers I'm still not convinced there is any tank there at all. If there is a tank it could also have concrete covers often two. If that is the septic tank pictured where is the percolation area and manhole cover for the pipework that feeds it?

funnyname

Thanks for the replies, I'm away until tomorrow so will post a few more pictures then.

However from memory those manhole covers near the timber casing are the only ones around.

I also know the previous owner had to dig out a new channel perpendicular to the timber cladding, to the percolation area I guess.

The house is on an acre so plenty of space for a percolating area.

Also on and off over the last few months there's been bad smells coming from some of the drains in the house, sink, bath, etc. Not constant but there every so often.

Would the bad rain over the last few months be causing an issue?

If we need to get it drained would the manhole that looked blocked be the one to empty it from?

my3cents

The rain could have been the reason for any worse than usual smells. The extra water can dump untreated waste directly into the percolation area.

The diagram here https://sargunan7.wordpress.com/2010/01/25/septic-tanks-types-of-toilet/ is like many septic tanks. The biggest variation being the internal baffles and the number of manhole access points. A lot of septic tanks have a man sized manhole cover at each end so you have access to either side of the baffle.

Beyond the tank the outlet goes to a distribution box which feeds the pipes in the percolation area.

So far with your system we haven't see the top of the septic tank with its manhole cover(s) and haven't seen the distribution box.

funnyname

I dug the soil out a bit at the top and found this stone cap, is that what needs to be removed to desludge it?

my3cents

OK so that looks like your septic tank, but I don't see any obvious way into it? You need to dig around the edges to see if that slab of concrete with the slots in it is actually the cover and can easily be removed.

funnyname

Yeah I did a bit more digging and I can see the edges of that slab lid.

Back when we originally viewed the house a spoke to the owner and he mentioned that they only used eco-friendly washing up, washing detergent etc. So looking at the cover slab of the tank vs the way the timber cover is he probably never intended to have to empty it.

I'll attach another photo when I get a chance.

my3cents

funnyname wrote: »

Yeah I did a bit more digging and I can see the edges of that slab lid.

Back when we originally viewed the house a spoke to the owner and he mentioned that they only used eco-friendly washing up, washing detergent etc. So looking at the cover slab of the tank vs the way the timber cover is he probably never intended to have to empty it.

I'll attach another photo when I get a chance.

Don't whatever you do use biological washing powder as then you go the other way and destroy the septic nature of the tank and end up with a cess pit which needs regular cleaning.

If you want to check if it needs emptying here is some good information http://extension.missouri.edu/p/EQ401 . I know its american but S H One T is the same the world over. The section on System Maintenance is just over 3/4 of the way down the page. Also some good information on how often you should be thinking about getting the tank emptied according to the tanks use and size of household.

With regard to your original question about putting soil over the tank, then you really need to build up the section where the lid is and bring that up to ground level for easy access in future then you can fill in the rest. You don't have to reuse the concrete cover and can use an easier to open metal manhole cover and surround. Put mesh vents on the top of the pipes that stick out of the ground and make them obvious so you don't mow over them.

funnyname

We've been pretty good over the last 18 months re non-bio washing powder/liquid but I'd say there's been a few bio products bought so I guess that hasn't helped. Is there a way of regenerating the septic nature of the tank after we get it emptied?

Re the cover I think the ventilation tube is too close to it to build up around it

Nekarsulm

The traditional method of refreshing or rejuvenating a septic tank was to throw the carcase of a hen into it.
No doubt you can buy some product with billions of "bugs" in to do the same job.

Bonzo Delaney

Nekarsulm wrote: »

The traditional method of refreshing or rejuvenating a septic tank was to throw the carcase of a hen into it.
No doubt you can buy some product with billions of "bugs" in to do the same job.

Can't remember if I read it here or another forum but someone suggested buying a kg of cheap mince leave it out side in the sun for a while a week maybe plenty of bugs then.
Then flush it down the toilet. That way it'll go directly to the bottom of the tank
And save breaking the crust layer in the tank.

funnyname

So I got it emptied and the smell in the house is gone. Now I want to get rid of the rotting timber casing around it.

I was thinking that I could get a steel frame made to around the edge of where the concrete caps are and then have a steel manhole (with a lock type system for security to prevent kids playing with it) cover on top of this instead. Then I could fill in around the frames and bring it back up to ordinary ground level.

So just wondering re waterproofing this at the bottom of the frame so that rain water wouldn't get in and how to keep the frame flush with the opening while the area is backfilled?

Any ideas, suggestions on how to do this or ideas something else to make it safe as the timber frame has to go.

my3cents

Simple enough just build up around the manhole and make a new manhole at soil level. lengthen any of the vents to bring them up to soil level an then back fill with top soil.

You might even find that you can get some precast concrete "rings" or rectangles that will make leveling up the manhole simpler.

funnyname

I think the space between the manhole and the vent is too narrow to build it up with blocks, hence my idea of a steel frame. I'll look into the pre-cast rings.

my3cents

Cut the vent down so a right angle fitting fits flush with the top of the septic tank then use what ever fittings needed to bring the vent to the surface (couple of bit of pipe and another right angle). Then you can put your block work right up to and then over the top of the vent.

To make it easier to empty in future either get rid of the existing manhole cover or keep the block work well back away from the existing cover (so you have plenty of room to get at it to open it) and use a much larger one on top of the blocks. With the existing cover in place a couple of slabs on blockwork would do