Issues - biocycle unit, sewer smell in bathroom

Plek Trum

Hi all,
Would really appreciate experienced advice on this please.
Detached house with biocycle unit (Made by Eco Tanks), severe intermittent sewer smell appearing off and on in bathroom off child's bedroom.

Work done to date on this issue to try and fix smell:

All drains checked and clear.
Biocycle unit emptied (2nd time in 12 months)
Trap in shower resealed.
Trap in shower then completely replaced
Seals around toilet stripped and replaced
Shower ran daily, water always in traps
Biocycle unit checked - running fine.

Smell worse after heavy rainfall.
Smell back today after a good week or more of it being gone - we had heavy rain last night, coincidence?

We have now been advised to put a vent pipe on the exterior of the house, attached to the pipework that carries all waste water from that bathroom. In fairness, there is one running off waste water pipe from main ensuite, which extends to slightly above the rain gutter level, about 1ft above last row of tiles.

How can the smell be appearing in bathroom with everything sealed? I do feel it's coming from the shower hole (spent time on my hands and knees sniffing as last resort!) There is water in the trap and everything has been resealed.

The smell is not blowing back in the dormer skylight from the existing vent pipe as it appears when window is closed also.

Adding vent pipe does not address as to why this is happening repeatedly?? I'm tired and broke from paying different tradesmen to come and assess and "fix" the issue.

Would you recommend investigating anywhere else.

Bathroom floor and around shower tray all tiled.

The issues with the smell in the bathroom began a day or so after the shower was plunged with standard hand plunger to relieve a blockage / slow drainage from the shower. Linked??

Wits end - help really appreciated.😧😠

sky6

It sounds like your Percolation area is not functioning 100% and may need to be replaced. The fact that the problem is worse when it rains is another indicator.
Is there a vent pipe directly off the Bio Cyl.
How Far is the Bio Cyl from the House.
You could install an Intercepting Trap outside of the House which will prevent any smells reaching the House. However this will do nothing for the problem if it is the Septic Tank.

my3cents

The rain if too much of it goes down to the tank or if the ground water level floods the tank can push sewage out down to the percolation pipes and mess them up. That can create a stink but it shouldn't be that noticeable if there is a well placed stench pipe to take the odors away down wind.

Our neighbors have this system and I noticed only this week that the overflow that shouldn't really be there at the end of their percolation system is dumping a bit of raw sewage out of it, probably due to rainwater going into the tank and the percolation area being very wet. They don't have have any smells in the house however.

What you have is really just a septic tank with an air pump to speed up the break down of waste and I don't see why it would need emptying twice a year unless you go totally mad with household cleaners, biological washing powder and the wrong sort of toilet ducks. If for example you are pouring bleach down the drains everyday to stop the smell then you could be creating the problem.

However the system could also be messed up if there is too much water going down it and if the percolation area is polluted then thats another issue to fix.

A few of problems I have seen are related to the way the pipes are laid. I have seen underground waste pipes that are laid level (or worse) that hold waste material in them so you get the full on septic tank smell created in the drain.

Another classic fail is that the waste goes into the tank at the same level or lower level than the out flow to the percolation area. In that case you again get waste trapped in the pipes going into the tank. I have seen septic tanks connected up the wrong way because they were put in back to front with inlet used as outlet, outlet used as inlet so I can easily imagine any system could be put in incorrectly even a biocycle.

A third is where a blockage that is subsequently cleared causes waste to go back up into sections of drains that are rarely used so until everything has been flushed out, the smell continues - normally goes eventually unless there is another blockage.

So the things I'd check are:

1) YOU - what are you putting down the drains?
2) Rain water - where does it go? If you can get any covers off easily can you see if water goes down to the tank when it rains?
3) Is the percolation pipes/area damaged. If you have a manhole cover over the distribution box (if you have one) for the percolation area check whats down there. Should be "grey" water if its black sludge something has gone wrong. Again check if flow increases here when it rains.
4) Work out where every drain goes, fill from a hose or flush to check it really does run where expected and as expected. You might notice a long delay in the flow of some pipes if they are badly laid to the wrong grade. I did read here of a new house where the toilet was connected to the radon sump and it was in use a long time before the problem was noticed!