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Discuss Septic Tank Blockages in the Plumbing Forum area at UKPlumbersForums.co.uk.

  1. Paul Macmillan

    Paul Macmillan New Member

    I've had two blockages in the last 6 months in the drains leading to a septic tank which I unblocked myself with rods. The septic tank is a fibreglass Klargester and is about 30 years old. The drains are similar and are plastic.

    The blockage seems to be at the point where the drain enters the septic tank.

    Two blockages in 6 months worries me. I've lived in the house for 15 years and had no problems. Is it a sign that there is a problem in the drain/septic tank that needs addressing? Should I be getting it investigated?

    I don't think I'm putting anything different down the drains.
  2. ShaunCorbs

    ShaunCorbs S. Mod Trusted Plumber GSR Top Contributor!!

    Is there a build up around the exit to the Sep ?

    Have you changed any of your toilets / any internals ?
  3. Chuck

    Chuck Well-Known Member

    Assuming you really haven't changed usage recently...

    Joints like that are likely locations for breaks and leaks. Leaks attract roots. Roots cause blockages.

    When you unblocked it, did you have a chance to pull the blockage out and perform a post mortem to see if there were roots tangled up in it?

    If not, the risk that raw sewage is seeping out of a crack would be enough for me to want to investigate, e.g. a drain camera.
    • Agree Agree x 1
    Last edited: Nov 30, 2018
  4. snowhead

    snowhead Plumber

    The most likely issue is the Septic tank has moved away from the inlet pipe.
    Either the tank has settled down slightly or it's moved sideways slightly, in either case enough to separate the joint.

    As above a camera survey is needed, then corrective works.
    If it has separated then it will need excavation down to the pipe and a short piece of pipe joining in.

    If anyone suggests lining it, insist on an excavation or you'll be unblocking it regularly for evermore.
    I've seen several liners put in and they've all failed.
    • Like Like x 1
    • Agree Agree x 1
  5. DAVE01

    DAVE01 Member

    Best Form of septic tank is one made of solid blocks plastered inside and out side with a shelf to catch the solids and if you were doing it to the letter of the law no waste from sinks and basins Greece especially as this will not break down the solids which you need to happen As a matter of fact a old guy that I served my time with you should able to drink the water that comes out of over flow from a septic tank rather him than me Rather than using all these liners why don't you dig a couple of feet back on earth in ware pipe a use what is called a 6 x 4 Timble and out of the 4 inch side or 100mm side use PVC to know weather you have a bad joint use a 3 inch rubber ball and roll it down pipe this way you know weather pipe is level and no joint is fouled up only reel way to lay a sewer of any size is use boneing rods lay concrete from start to invert level this is how you have a built in fall in concrete just lay pipe on top job is a good one I would say the way your sewer was installed it was just put down on soil all very well in theory but over time it has sagged or even sprung a joint ? Best of luck Dave01
    • Funny Funny x 1
  6. Paul Macmillan

    Paul Macmillan New Member

    Thank you for all your advice- and the speed of them!

    From what you've said, I suspect it may be roots in the joint. It wasn't easy to unblock and the best I managed was pushing the obstruction away. I also have some plants near it that may have roots that have got in.

    I also suspect the septic tank has moved slightly as I had to raise the lid slightly a few years ago to get it to fit snug.

    Can I ask two questions please?

    1. Do you recommend getting an expert in or is this something I could do? Digging down and joining a pipe doesn't sound too tricky but I'm very happy to pay for an expert to do it.

    2. For the future, I'm a keen gardener and have planted things along the course of the drainage pipe up to the septic tank (I haven't put anything near the outlet of it or the soakaway). Do you recommend that I dig these up? Are small plants ok, just not trees/conifers?
  7. Rob Foster

    Rob Foster Top Contributor!!

    Have a go yourself, dig away expose the pipe take some piccys post in here , save some dosh for Xmas, do it soon frosty ground is no fun good luck Rob Foster aka centralheatking
    • Agree Agree x 1
  8. Chuck

    Chuck Well-Known Member

    Small plants should be fine. Roots are not usually the cause of the problem. Once there is a leak, e.g. due to ground movement or shrinkage, they will get drawn towards the wet and once they've found their way inside the pipe act as a snagging point for the blockage to form.

    With larger plants and trees, I believe that they don't directly cause damage because roots don't AFAIK try and drill through solid objects like pipes. The problem is really that they cause the ground to move and shrink by drinking the water in it. This action strains the pipework and joints, etc.
    • Agree Agree x 1
  9. Pickwickpick

    Pickwickpick Plumber

    As @Chuck@Chuck says the problem with roots comes from the ground shrinkage when they suck too much water out of the ground causing movement that damages the pipe work, they then head into any cracks and cause even more damage.

    Small shrubs, vegetables, flowers... aren't going to cause any problems, trees are the main culprit but it does depend on the type of tree. You don't want a Weeping Willow anywhere near any pipework but something like a small Crab Apple shouldn't cause any problems even if planted near house/pipework. If you're planning on planting any trees you can use google to find recommendations of minimum distances specific trees need to be kept from house and that would be a good rule of thumb for how far to keep them from your tank. Its always worth a double check as some can be quite surprising, e.g. Acers which are pretty delicate trees that you wouldn't necessarily assume would be problematic are generally best kept fairly far away from pipes.
  10. Paul Macmillan

    Paul Macmillan New Member

    Thought I'd better give an update to my problem as I always find these forums really useful.

    I dug down (which was very easy and only took about an hour) and roots weren't an issue. The ground has thick clay from about 15cm down and the roots didn't go beyond this. The problem was that the septic tank had sunk (the drain piping was set into concrete so hadn't moved). This had caused the pipes to come apart slightly at the top but more significantly the pipe into the septic tank had disformed due to it sinking but still resting slightly on concrete. This was causing the blockages.

    I cut the disformed pipe away and joined it to the drain pipe with a piece of pipe and two rubber joining parts. It's working fine now but I am a little concerned I may be kicking the can down the road. If the septic tank continues to sink it's going to come apart again so I'm hoping it's not going to!
    • Like Like x 2
  11. snowhead

    snowhead Plumber

    Glad it's sorted.
    The movement was probably just initial settlement over the 15 years.
    At least you'll know where to look if it does block again.
    • Like Like x 1
    • Agree Agree x 1
  12. Rob Foster

    Rob Foster Top Contributor!!

    Well done, you have saved yourself a small fortune and fed back to us...thank you. Rob Foster aka centralheatking
    • Agree Agree x 1
  13. Pickwickpick

    Pickwickpick Plumber

    Thanks for updating us and that's great news. Its not likely to be an ongoing issue.
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