Extension - build over 60s drains or replace

[23vc]

Hi
General question, appreciate it's probably an obvious answer though
Doing my extension at the moment and there are existing drain runs which will end up built over IE under the slab. There is an existing manhole which will still be outside so can stay as is.
I am thinking I can either keep the existing lines and break into them as appropriate and get it camera'd to make sure no existing issues anywhere (all subject to bco approval obviously) or do more digging, expose and replace anything that will end up being built over (IE replace anything within about a foot of the feed into the existing manhole)
Appreciate any advice, I know it's a bit of a noddy one

PS none of these are shared with anyone else

Cheers
John

 

[Ian H]

I'd replace them outside of the new building. At that age they could be nightmare pitch fibre, even if the manhole has a clay channel.

 

[nickjb]

I replaced the lot when I did mine. The building inspector was happy for them to stay but the first couple of bits I exposed were cracked at the joint. A bit more digging and each section had a hairline crack. Much happier knowing it's a continuous run of new plastic.

After the build we had an issue with rats. The neighbour, who had a similar extension about the same time, was convinced they were coming from us partly because I'd DIY'd it so may have done it wrong. She paid for a drain inspection. Turned out mine was perfect and her builder had left all the original drains in and had a disused branch that wasn't capped.

 

[23vc]

Thanks guys appreciated