Septic Tank Issue - Kingspan Bioficient 1 - Sediment/Sludge in clean zone/soakaway - Lost its shape

[Mackrellfishing]

Hi all, 

 

I bought a brand new house in 2019 from a small local builder. The house has a Kingspan septic tank and lately I have been having some issues with it. Kingspan completed their annual service in August 2024 and the engineer noticed that the inspection chamber before the tank was completely blocked. He cleared the blockage and he noted in his report that there are signs that the tank has "shifted" and this may be causing the blockages. I say blockages as over the past few years that chamber has blocked on occasion and I cleared it as normal. To be honest, I didn't think anything of it. 

 

Fast forward to November 2024, Kingspan emptied and entered the tank to check if the tank has lost its shape. They confirmed that it has not lost its shape in the primary settlement chamber. They could not confirm if it lost its shape in the aeration chambers as they can't be emptied. I was extremely disappointed in this inspection, Kingspan charged a hefty fee for this and the engineer was taking levels using a small level (the type that comes with a TV bracket) sitting on a two inch pipe spanning across the lid of the tank. Completely unprofessional and the fee unjustified in my opinion. The report did not include any definite measurements of how much it has moved or what way it has moved other than "there are signs the tank has moved from installation"... the exact same conclusion as they stated in August 2024. I must note that they stated if the tank moved, it may have kinked the pipe between the final inspection chamber and the tank. I dug down to the pipe and I can confirm the pipe is not kinked at all. The length of the pipe from the final inspection chamber to the inlet of the tank is only 1 or 2ft. 

 

One of the key things that the Kingspan engineers keep saying is that the internal baffles of the tank are bowing which is an indicator that the tank has lost its shape, but in my early days of living here, when I looked in the tank myself, I could see the baffles bowing. Again, I didn't think anything of it as I assumed that a plastic baffle would bend slightly with the water pressure/weight behind it. My question to Kingspan is, they have serviced the tank annually since 2019, why did they not flag the issue with the baffles bowing in the early days when the tank and house was still under warranty. I also want to note, as soon as I confirmed to the engineers that the pipe was not kinked, they started stating it has lost its shape with the reasoning being the bowed baffles. The builder backfilled it with pea gravel as per the Kingspan Installation guidelines at the time but what is interesting, is that Kingspan now state that the tanks need to be backfilled with concrete....

 

Furthermore, there appears to be sludge and/or sediment in the inspection chamber on the clean side heading to the soakaway and also a fair amount in the final settlement chamber inside the tank. The Kingspan engineers have said that the sediment/sludge in the soakaway can be a sign that the tank is not functioning correctly due to the movement of the tank causing a blockage and when the blockage clears itself, it is overloading the tank and forcing everything through the tank too quick. I know for a fact that there is nearly always sediment/sludge in the soakaway and I can confirm that during their previous inspections over the years, there has been sediment/sludge in the soakaway and again, Kingspan never raised it as an issue or stated it may be a sign of a tank issue until August 2024. At the minute, I am in limbo and Kingspan are saying the entire tank needs to be exposed as the next step.  

 

I would much appreciate if anyone else has had the same issue with a tank of any brand that has "lost its shape" or has sediment/sludge in the clean side heading to the soakaway and what came of it or in general, if someone has any comments or advice. 

 

Thank you all for your time and comments in advance. 

 

If any of the readers would like, I can go into detail on how I believe the tank is overall, just a bad design and I can show evidence of this if needs be. I don't want to expand on this post so you don't all lose interest. I can also show and tell how the Kingspan engineer actually cut out the curved dip pipe inside the primary settlement chamber as they stated this can sometimes cause blockages...there seems to be a lot more to this shafted tank than I initially thought... 

[crooksey]

Tanks come with a guarantee, if its lost its shape, its on them to prove its through no manufacturing fault.

 

This is why building control exists, they would have had to guarantee and oversee the installation of a new tank is done correctly. I would suggest speaking to the small local builder and his building controller as a first point of call.

[ProDave]

2 hours ago, Mackrellfishing said:

I must note that they stated if the tank moved, it may have kinked the pipe between the final inspection chamber and the tank. I dug down to the pipe and I can confirm the pipe is not kinked at all. The length of the pipe from the final inspection chamber to the inlet of the tank is only 1 or 2ft. 

....

 

I also want to note, as soon as I confirmed to the engineers that the pipe was not kinked, they started stating it has lost its shape with the reasoning being the bowed baffles. The builder backfilled it with pea gravel as per the Kingspan Installation guidelines at the time but what is interesting, is that Kingspan now state that the tanks need to be backfilled with concrete....

So you exposed the pipe between the final inspection chamber and the inlet of the TP and confirmed it was not kinked.  Did you put a spirit level on that pipe when exposed?  It must run downhill from the IC to the TP.  We need to know if that is the case.

 

If it does run downhill and the IC is not emptying completely, then the TP is filling too full.  That could be because it is not level, or it could be an internal baffle has distorted.  The baffles usually form a weir between the dirty and clean side of the TP.

 

As for  backfilling with pea gravel.  That might be okay it might not.  At a previous house the installer badly advised me and set a septic tank in pea gravel.  The site has a high water table in winter, so if the tank was desludged (emptied) in winter there would be a very real chance the tank could float out.  I dealt with the situation by only ever getting the tank desludged in the middle of summer.  Even if it did not float out, it could possibly move if emptied at the wrong time.

[Mackrellfishing]

@ProDave Thanks for the reply. 

 

Yes, I exposed the pipe between the final inspection chamber and the tank, it was not kinked and I did stick a level on it to make sure the fall was correct. 

 

The point I am trying to make with regards to the pea gravel is that the Kingspan guidelines at the time stated if could be installed with pea gravel which is what the contractor did but now, the Kingspan guidelines state that all septic tanks need to be backfilled with concrete (so the Kingspan engineer says). They don't even produce my tank anymore. 

 

The baffle between the primary settlement tank and the first aerator is definitely out of shape, but if has been out of shape since I moved in. I.e i can remember looking into the tank in the early days and seeing it bowed but I didn't think anything of it. Kingspan have also serviced it annually since 2019 and never raised it as problem until now.

[Mackrellfishing]

@crooksey Thanks for the reply. Unfortunately the tank is out of warranty. The house did come with full building control sign off. I am in NI so our building control is completed by our local council directly. 

 

Nice point about them having to prove it wasn't a manufacturing fault, I will see what I can do with this as I have pictures from back in the day (when it would have been in warranty) showing the baffle bowed. 

[saveasteading]

The building inspector is not responsible. They do spot checks not supervision.

The builder may still have liability. Check the contract.

If KS now want a concrete surround, then that sounds as if these tanks are now known to need it. 

Their inspection is not going to be independent.

[ProDave]

I bet the instructions said use pea gravel only if not prone to high water table?  

 

Lets reset the conversation, apart from the occasional blockage between the final IC and the input to the TP, what is the actual "issue" you are trying to solve?