House Purchase - Drainage Inspection

thias

We're in the process of purchasing a house. It's approx 170 years old 4 bedroom detached. We've had a RICS Building Survey carried out by a local independent surveyor who called out some movement down one side of the building, which we had already noticed. The surveyor believed this to be historical, but recommended a CCTV drainage inspection to rule out anything more sinister, just in case.
With the vendor's permission, we instructed a local drainage company to carry out a CCTV inspection, apparently the house actually has two drainage systems, the original, which is in need of replacing and a second, more recent system which services an extended part of the building, which is also the same area as the movement has been found. When the company came to inspect the more recent system they were unable to as apparently one of the drainage junctions has been fitted the wrong way around so their cameras couldn't be guided through the pipes correctly. They've offered to excavate the junction, flip it around, make right the area and complete the inspection, for a cost of course, which I'm willing the foot, however the vendors are reluctant to have this carried out until the purchase is completed.

1. Has anyone else heard of a CCTV inspection not being possible because of a junction being the wrong way around?
   
2. Is there any other way we can inspect the drains? I guess something else must have been used prior to the invention of CCTV inspections?
   
3. Am I right to insist on this before proceeding with the purchase given the potential impact of the structural movement in the same area?
   

Thanks!

princeofpounds

1. Not heard of it - it would be helpful to get a bit more explanation about what they mean by this, but I can only imagine that they are required to turn a sharp corner, almost back on themselves. There are plenty of reasons why a CCTV inspection can be blocked but it's just hard to know what specifically the issue is.

2. Well, normally you would try other access points - I presume they did this. It's unusual not to have any other options, at least part-way, however. You can test flow with dyed water, but that doesn't tell you much about structural condition.

3. Probably, if it really is causing structural issues. If I were the vendors, I'd jump at somebody paying to fix this unless it was hugely disruptive. It's quite possible they will have the same issue with future buyers if the movement is quite evident.

However, if the existing survey already shows a significant part of the system needs replacing then you can always just assume that you'll have to do this part and factor it in to your offer anyway. The risk there is if the movement is being caused by something else (although drains are a common culprit)