Smelly Septic Tank

[Daf]

I have replaced an old onion septic tank and a drainfield that was no more than a hole with builders rubble (done before I owned the house) with Graf Carat 3750L and a drain field that in total is around 56m long and 0.9m wide. The system has been up and running for around a month and seems to be working well. However, I am getting some strong whiffs of foul gasses coming from the tank manhole and other manholes in the system. I know that I can buy a sealed manhole cover or use some manhole grease to seal the drains but that is a work around and probably not the cure. The soil stack vent attached to the house must be a total of 30m away from the septic tank, given the soil pipe run. I could improve that a bit by adding a rotary cowl to encourage venting at that level but it was OK with the previous onion tank.

 

I am wondering whether I need to wait for the tank to settle down or whether I need to commission it somehow? I'm not chucking a dead cat down there, not sure about these wonder chemicals for sale on dodgy websites and unsure as to chucking bicarbonate of soda down the toilet would help. Has anyone experience something similar?

[Cpd]

https://www.muck-munchers.co.uk/product/septic-tank-treatment/?gclid=EAIaIQobChMI7vnip9bT-QIV5ejtCh3tEA41EAAYASAAEgJdr_D_BwE
 

i put in a replacement septic tank a few years ago ago a use this stuff monthly, works great. I put a carbon filter over the vent pipe but not sure it’s needed now. I am very careful not to put anything down the drains that will upset the system, no bleaches or nasty chemicals as I use septic tank friendly cleaning products including dishwashing tablets and cloths washing liquid. 

[saveasteading]

There is digestion going on in the  tank and gases are likely to need an exit, so probably best to choose the least nuisancy point and leave a gap there.

My understanding is that a balance isn't reached for quite a few weeks.

3 hours ago, Cpd said:

no bleaches or nasty chemicals

But also, the tank will be designed for a balance of contents, so  pee, poo and water basically. In a normal household that will balance out. But if there is an imbalance eg rainwater getting in, or not enough water, then it may get whiffy.

[Daf]

18 hours ago, Cpd said:

https://www.muck-munchers.co.uk/product/septic-tank-treatment/?gclid=EAIaIQobChMI7vnip9bT-QIV5ejtCh3tEA41EAAYASAAEgJdr_D_BwE
 

i put in a replacement septic tank a few years ago ago a use this stuff monthly, works great. I put a carbon filter over the vent pipe but not sure it’s needed now. I am very careful not to put anything down the drains that will upset the system, no bleaches or nasty chemicals as I use septic tank friendly cleaning products including dishwashing tablets and cloths washing liquid. 

Thanks for the info. I've bought it, to see if it is a quick fix before the tank establishes itself.

 

Bleach is a septic tank killer but you can use it in small quantities. It seems that since 2017 (EU legislation) most washing powders and dishwasher tablets are now phosphate and bleach free, so should not be harmful to any tank.

[Daf]

14 hours ago, saveasteading said:

There is digestion going on in the  tank and gases are likely to need an exit, so probably best to choose the least nuisancy point and leave a gap there.

My understanding is that a balance isn't reached for quite a few weeks.

But also, the tank will be designed for a balance of contents, so  pee, poo and water basically. In a normal household that will balance out. But if there is an imbalance eg rainwater getting in, or not enough water, then it may get whiffy.

I never had a problem with smell from my previous onion tank. That was a loose lid sitting on top of a breeze block chamber. Nowhere near air tight. I assumed that all smells were vented through the soil pipe stack attached to the house, at the end of a 30m run?!

 

I think you are right about having to wait for it to establish itself. I never fully emptied the old tank and always left at least a foot of sludge at the bottom. No rainwater goes into the tank but it was filled with clean water during installation so that the pea gravel that surrounds it, could be distributed evenly and tamped down. So, the idea that the tank currently has too much water in it, err, holds water!

[JohnMo]

On 19/08/2022 at 20:54, Cpd said:

https://www.muck-munchers.co.uk/product/septic-tank-treatment/?gclid=EAIaIQobChMI7vnip9bT-QIV5ejtCh3tEA41EAAYASAAEgJdr_D_BwE
 

i put in a replacement septic tank a few years ago ago a use this stuff monthly, works great. I put a carbon filter over the vent pipe but not sure it’s needed now. I am very careful not to put anything down the drains that will upset the system, no bleaches or nasty chemicals as I use septic tank friendly cleaning products including dishwashing tablets and cloths washing liquid. 

Just order a year's supply of muck muchers.  My soil stack is about 50m away from the treatment plant at the end of the house (single storey) and only about 3m in the air. If the wind is blowing in the wrong direction it can be a bit smelly.  

 

Worth a go for £39 delivered.

[Daf]

Well, either the tank has established itself or the Muck Munchers I put in, a week last Monday, has worked. There have been wafts of stinky air about the place (especially near the tanks) for several weeks. At the moment there is no smell of anything in the air at all - even when I'm up close to the tank and the manholes. I think that anyone who is putting in a new tank should think about starting it off with a year's supply of these.

 

Admittedly, I thought this was going to be some snake oil stuff but it seems to be working. If anything changes I'll report back.

 

[ProDave]

The local "advice" here is when starting up a new tank, drop a dead rabbit into it.

[saveasteading]

I have put in 2 in the past. We connected the site toilet temporarily which perhaps gave it a low use start, and then the main buildings when ready. No problems at all, so it seems there are enough microbes or whatever without buying any.