Septic tank smell

[Dr1Gonzo]

Fairly new house so the septic tank shouldn't need cleaning.
Every day there is a smell coming up through the floor pipes in the house - are these the vent pipes?
I had thought that vent pipes were only supposed to be on the roof.
All the sinks and toilets in the house have s bends so the smell cannot be coming through those.
There are
2 floor pipe drain holes in the upstairs bathrooms,
1 floor pipe drain hole in a middle floor bathroom and
1 floor pipe drain hole in the bottom of the house

All have a smell coming out of them but only occasionally...definitely first thing in the morning and at nightime but a little bit during the day...seems to clear a bit during the day but could just be because doors are open. Sealant could be cut if access was ever needed.

Can't these drain holes just be sealed around the rim with sealant therefore forcing any sceptic tank air up through the roof?

[gus-lopez]

normally those floor drains drop straight into the top of the 4" soil pipe under the house, without any traps. That's why you get the smell come back up. Normally more pronounced if the wind gets up.
I'd be surprised if there is a vent pipe anywhere on the system, another reason it comes up the drains.

[Dr1Gonzo]

normally those floor drains drop straight into the top of the 4" soil pipe under the house, without any traps. That's why you get the smell come back up. Normally more pronounced if the wind gets up.
I'd be surprised if there is a vent pipe anywhere on the system, another reason it comes up the drains.

Sounds about right but.
When I say floor drains, they are not water drainage, they are just holes with a metal covering lid (cove plate, maybe it's a cleanout access hole?). No water ever goes down them.
It was the same with the washing machine but we managed to block that up with a fully sealed waste pipe so no smell from that anymore.
How else can you stop it apart from by sealing?

[barry]

Could be that the tank was connected to the house with no trap in the main pipe outside.

Spanish builders did this to our neighbours and it stunk for days until noticed.

[country boy]

One often overlooked possibilty is a dried out trap. Make sure there is a water seal in all traps...an unused Bidet is often a culprit or an unused shower tray/basin in a spare room.

[Dr1Gonzo]

One often overlooked possibilty is a dried out trap. Make sure there is a water seal in all traps...an unused Bidet is often a culprit or an unused shower tray/basin in a spare room.

I'll that and fill the floor covers.
What are the floor covers for anyway? Are they just there to clear the pipes? Clearing holes?

[Donz.]

handy thread this! I always wondered what the covers were for too!

Also, does anybody know of companies in the Malaga area that you can contract to come and empty your tank?

[USINSPAIN]

I use Pepe Nunez they seems OK

[peteroldracer]

Under the metal cover should be a round polyethylene 'junction box' where all the drains meet, before going off to the fosa septica. This should be sealed, with a rubber sealing ring, and act as a water trap. The cap may be taken off (carefully) for cleaning out any gunge that has become trapped in there - clumps of hair can be a problem, and can act like a wick, draining the water and stopping the trap action. This 'gunge' can also be in the shower drains, with the same affect...long haired ladies cause more trouble than balding old gits!

[Donz.]

USINSPAIN do you have contact details please / website / email? thanks

UPDATED - NO NEED THANKS JUST FOUND THEIR WEBSITE

[El Cid]

These floor traps do not usually connect to a proper U-bend but have a crude water trap where the water acts as a barrier. It probably works OK in a shower which is constantly filled with water but the one in the floor hopefully never gets any water in it so it doesn't work at all or if there was water in it, it rapidly evaporates.

We had a huge U-bend fitted in the main drain pipe before it goes off to the septic tank. This improved things enormously as we were getting smells from minor things like the overflow holes in the sink, bidet and bath which didn't seem to go through the U-bend.

Sid

[Dr1Gonzo]

These floor traps do not usually connect to a proper U-bend but have a crude water trap where the water acts as a barrier. It probably works OK in a shower which is constantly filled with water but the one in the floor hopefully never gets any water in it so it doesn't work at all or if there was water in it, it rapidly evaporates.

We had a huge U-bend fitted in the main drain pipe before it goes off to the septic tank. This improved things enormously as we were getting smells from minor things like the overflow holes in the sink, bidet and bath which didn't seem to go through the U-bend.

Sid

I opened the floor cap up again and turned on the tap, which caused it to gurgle a bit.
It looks like the water gets into it somehow and runs down another smaller pipe but there is no water barrier at all.
Would sealing the floor caps stop the smell? Just run sealant around it and or put plumbing putty on the rubber ring that is trying to plug the current hole?
There are 4 floor holes (clearing access drains) in the house - when opened each of them stinks but there is no problem from any of the taps or basins in the house, which all look they have p traps. I am not sure about whether the shower drains have p traps or not.

[gus-lopez]

Another thing worth looking at, if the smell remains after sealing the floor covers is the Spanish used to have a habit of not connecting the toilet pan physically by pipe to the soil pipe. They would just position it over the hole & save themselves the expense & work of installing concentric/eccentric connectors. It rarely happens now, although I have seen it once a few years ago. This means that the pan is relying solely on the silicon sealant , if there actually is any, to the floor to prevent smell ingress.

[Dr1Gonzo]

So, if I block up all the floor holes, where is the gas from the septic tank supposed to go?

[country boy]

It should be vented, from the tank. The tank is a living biosphere, air needs to get in also, bugs need it!

[chrissiehope]

The vent point may not be very close to the tank - ours is about 6 m away, hiding in the middle of a big olive tree

[gus-lopez]

In the old days they never fitted vents, just relying on air getting in/out around the rough old concrete cover.
When I fitted a new metal cover & frame to mine I dug the pipe out & cut & fitted a vent in.

[Dr1Gonzo]

So, I sealed the floor covers - that has improved.
Although now what happens is that the stink is coming through the aircon central vents in the house.
I can only think that
- the middle wall in the house (where all the cables and ducting come from the roof) either has a non-sealed pipe
- the aircon condensation drain might be plugged into the main drainage pipe?
- the vent for the septic tank is running through the middle of the house up to the roof but I doubt that.

[gus-lopez]

Might be time for a crawl around under the house to see what's what ?

[Dr1Gonzo]

Under the metal cover should be a round polyethylene 'junction box' where all the drains meet, before going off to the fosa septica. This should be sealed, with a rubber sealing ring, and act as a water trap. The cap may be taken off (carefully) for cleaning out any gunge that has become trapped in there - clumps of hair can be a problem, and can act like a wick, draining the water and stopping the trap action. This 'gunge' can also be in the shower drains, with the same affect...long haired ladies cause more trouble than balding old gits!

It had a plug seal under the metal cover but I sealed that up further with sealant.
The smell from the metal covers has now stopped but it's still coming through the middle of the house.
I lifted up the ceiling tiles of the toilet room in the middle of the house (where the vents are hidden) and there is a strong stench of sewage so the smell is still leaking out somewhere. Only other thing I can think of is that sewage is actually leaking out of a broken pipe or someone drille dinto a pipe but there are no water leaks in the house/ceilings/floors of other rooms so it seems more like an air leak than a liquid leak.

These floor traps do not usually connect to a proper U-bend but have a crude water trap where the water acts as a barrier. It probably works OK in a shower which is constantly filled with water but the one in the floor hopefully never gets any water in it so it doesn't work at all or if there was water in it, it rapidly evaporates.

We had a huge U-bend fitted in the main drain pipe before it goes off to the septic tank. This improved things enormously as we were getting smells from minor things like the overflow holes in the sink, bidet and bath which didn't seem to go through the U-bend.

Sid

Is it possible to fit a 200mm p trap? Most p traps are from the sink/toilet which are the 50mm types.
Would a big 200mm p trap have enough pressure to get water through the p part?

The ones in the floor all have water in them so maybe something behind the wall has an open pipe in or something? None of the sinks, bath, shower, etc. smell at all - it is only when you lift up the ceiling tiles in the toilet room to have a look down one of the main walls in the house (where all electricity pipes and drains are buried in the wall) that the smell occurs and therefore through the vents.