Need advice on sewage pipes

[Befals]

Buying an early 70s house, the survey picked up ground movement causing damage to the garage/concrete drive with cracking around the manhole cover. Suggested the cause could be tree roots or damaged sewage pipes and suggested we get a cctv survey. Got the results today which showed the pipe was holding water. The report said this suggested the pipe has moved and recommended replacing it.

Firstly any idea how much it is likely to cost to replace? (10m length of pipe) a quick Google suggests repair isn't too bad but replacement is likely to be quite pricey.

The other issue is whether the ground movement is caused by leaking water, or ground movement has caused the pipe to move. There are some fairly large trees in a neighbouring garden, but they are closer to the front of the property, and there were no roots visible in the pipe itself. If the pipe movement has been caused by ground movement, then I'm concerned that replacing won't solve the issue. Any advice?

Cracking around the manhole cover

If it's holding water are they saying it's not draining way, and if it is it's leaking out somewhere?
I only ask is our surface water drains don't have enough drop so the water sits in it, till it rains heavy enough to push the water down it.

Also that manhole cover looks new for a 70s house. What work has been done previously?
Are you sure it's not just that the concrete is naff and one small crack has just got bigger.

If that was me, personally I would budget for a new driveway, and factor in replacement in pipe. The sewage pipe itself is quite cheap, it's the labor and digging up that costs. But if u want a new driveway get it done at the same time.

110mm pipe is about £10 for 3m , plus connectors you need. So pipe and connectors wouldn't be more than £100 , it's the fact it's under all that concrete, and garage

@Fightingfirewithfire the report just says it's holding water (you can see it sitting in the pipe on the video) and that it's likely to be because it's moved ( I guess so it doesn't slope properly to move the water along). I did ask the EA about possible work to the manhole as the other one at the front is new but was told they'd replaced that as it had been driven over and broken but that the one in the back wasn't new. It's an inherited house though, although the son has been lIving there for a year since his dad died, and I think he may have been living with his dad before that.

The garage has really bad cracking on a diagonal on the left wall, and the wooden beams inside are twisted (reported in the survey- haven't seen myself) so recommended that we get a structural engineer to check it over. The surveyor said that it looks like ground movement likely from damage pipes or possible trees roots and the garage has moved because of shallow/no foundations.

We're not so fussed if the garage has to come down, but were concerned as to what the cause of the ground movement was. If it's caused by the pipe that fine and we can replace, it's whether it's caused by something else, and that has damaged the pipe that's my concern.

Those quotes are reassuring, my quick Googling was suggesting hundreds per meter of pipe replacement. I guess the biggest issue is digging through the concrete. Not fussed about replacing it as there's driveway space at the front of the house.

Honestly I'm not sure how you will know what has caused it till you dig down.

Id bet it's the tree roots, if the water is sitting there, it's not draining out to cause the ground to become soft (that's my thinking anyways), and I know you said the trees are at the front of next doors property, but if they are well established and big trees the roots will most likely be under your drive.
Our back neighbors have trees , and when they did our back extension they were finding roots 5" thick next to the house 9m away. We ended up needing 2m deep foundations.
We have just had so much fun doing our garden, think we spent much of our time removing roots (and I'm half surprised the trees haven't fell down as I swear it felt like we had the entire root system in our garden)

You could ask the neighbors if they have had any issues or if the previous owners mentioned any thing.

Do you know if it's your surface water that is just connecting to that manhole cover or is it all your drains.
If it's all, do you know where on the line you are.

For instance we are at the start of the drains, so all our pipes are closer to the surface than the others, so about 12" down, where as next door are about 20" down when you get to their manhole cover, and so on.

Just means you might have to dig down further, and if you are replacing pipe warn neighbors not to all start flushing their loos etc.

@Fightingfirewithfire with apologies @Befals, quick question, can rainwater pipes empty into same system as other waste water?
I thought this was contrary to building regs - but I know nothing, and you sound like you know a lot.

Well I believe it depends on when the house was built.
All the houses in our area are 50+ years old and all connect into the main sewer, as does all the extensions, our extension is 3 years old and connects into one, as that's what it did before, we just moved the pipes, which both building regs and the water board was happy with when they inspected. With the OP house being built in the 70s it probably is all into one.

I think new builds can no longer do this, and by new builds I mean on a completely new plot of land that hasn't had any drainage before.

I saw a recent planning application that was approved and also by building regs that was to knock down a commercial building (old community center) and build new houses there instead and the plans and all the correspondence said connect to existing drainage. So I'm assuming if the drainage is already there then it's ok. Even if it's a new building.

Thank you for clarification.

I've just checked the exact wording on the planning portal thingy re surface and foul and it says

There are two systems of drainage that you need to think about: 'foul' and 'surface water'. In general, these two systems should be kept separate

I think because the word should is there it's a bit open to interpretation.

Also if your surface water drains into a public sewer you get charges for it on your water bill. I'm pretty sure I've a surface water charge, but we had that before the extension