Small inspection hatch for pipe joint in concrete floor?

Maybe the kind of hatch you see in the street to allow access to water stop taps? Builders merchant?

Sometimes called a "toby"

An excellent suggestion but they all seem to be marked either "water" or "gas"

the ones for boats are neutral that way - and waterproof. But I don't know if they are up to being driven over. Eg

An aluminium rodding eye would give you a frame and cover but you?d need to saw off the angled pipe beneath. Just a thought.

Thanks Tim, I think that will fit the bill nicely so you've just won the prize :-)

Is it practical to dig up the whole length of the pipe and replace it with a longer one with a bend in it?

It runs from a tank about 4m away from the house, under a hedge and dry stone wall, under two paving slabs, through cavity wall footings and across the 5m wide garage/workshop (in a screed-filled trench) ... perhaps I should call for volunteers ;-)

Would need a straight route though, unless you fancy hiring a ditch witch ...

On further thought, I decided this was the final justification for a 3D printer, so ordered a Prusa which is now partly assembled and waiting for me to allocate more time to it. Building the extruder was an "interesting" task and I'm in awe of the designer's skills. Unfortunately, the 3D printer route means I have to climb the Fusion 360 hill, and that looks very steep!