Can anyone interpret this drainage report from 1935?

[Fooferella]

I've had a guy in to dig trial pits to determine the depth of the public sewer out the back.
This is the original inspection of drains from when our house was built. Do any of you wise ones know what all those symbols mean on the report? We are number 42, second from left and I think the sewer is the line at the back (top of pic). Our structural engineer estimated the line at about 1.6m out from the back of the house but the workmen dug a good metre down today and found nothing.

Do any of these symbols give clues to how deep it is or the distance the line runs from the house? Any help appreciated!!

well I can tell you one thing 2 houses ago (!) the house we lived in was built in the 1960's when our builder (who also lived on our estate so he knew the area!) had to find the sewers for our extension - he said to me that from previous experience the estate plan showing where the sewers were bore no resemblance to where they were actually sited & it was the same throughout the estate - go figure!

I'm a total Newby at this. It only just occurred to me that the sewer might not follow the path of the drawing from so long ago! I've just been doing a bit more research on this and didn't realise that drains can be traced by sonar. I'm wondering if this is a solution?

find a manhole and look down it.

My dsis found her drains really accurately with divining rods.apparently lots of water companies use them.

I've looked down the manhole up the street but the eng said the depth might not be indicative as the manhole is on the flat but we're down a steep hill meaning each of the gardens are terraced. The depth of the sewer on entering and exiting the property might be different IYSWIM.
Come to think of it, the eng used divining rods the first time he visited so the pipe should be where he drew it. Would the sewer just be quite deep? Should I ask our guy to dig deeper? How deep might it be? The guys on his way and I've no idea what to tell him to do next!!
Thank you for all the replies so far (and the legendary Pigletjohn, I'm honoured!).

There looks to be a manhole at no. 44 so I'd knock on their door and ask nicely if you could look for it in their garden. If you lift that manhole up then you should be able to get a depth to the bottom (invert level). Generally people put drainage in as shallow a gradient as possible to minimise digging. The run is probably reasonably parallel with the buildings so I would start from there. Normally there is a manhole schedule that goes with the drawings indicating levels of the pipes at each of the manhole locations.

What are you trying to do?

Drainage could easily be more than 1m deep. Other option is to find where one of the pipes comes out of your house and dig along that until you hit the main drainage run. Would need to be careful not to break you pipe though.

Hi, I've found the engineers floor plans and rear elevation if that makes it any easier to determine where might the sewer be? The blue hatched area is floor level and concreted over. The grey hatched line is a 3 ft retaining wall. If the original plans say the sewer is 1.1m deep would it be from the floor level or from the higher ground behind the retaining wall? It would be quite a chore to dig all the way from the house to the sewer line but that may be the next step.

The handyman I hired keeps saying that his original pit is "1m as required" when I try to tell him that what is required is to find the f*ing pipe! He is a master at deflecting when I ask him to dig deeper.

OP your original plan seems to only have pipe sizes on it (4inch = 4" etc). I can't see anything that looks like a depth. If the ground is higher on the drain side then yes you will have to keep on digging. However finding out where 44's manhole is (to understand the likely line) and also lifting the cover to see depth is a really good idea.

It could be the invert level (gradient), diameter and depth of the sewer. The initials may relate to the type of drains ( culverts, surface water, land drainage, foul drainage or combined sewer).
All sewers serving just one house are private and won't necessarily be recorded by the water company. However pre 1937 sewers on private land that serve more than one house have always been deemed public and the water company should have maps.
----It's been over 10 years since I worked for a water company. Why do I remember all this?

Well, things have moved on. Our waste downpipe now has a mahoosive hole in it about 50cm down into the last pit so I've called out dyno rod, hoping for an engineer tomorrow so we don't have a raw sewage pit at the back door. The rep on the phone said they might be able to locate the blasted sewer when they come out.
@MrsMoastyToasty, are water records online like council records?

Looking at your plans, I would think that SP will indicate your soil pipe (did TP2 find that one?). SVP should be soil vent pipe. Can't decide if RP is rainwater pipe or rodding point. W could be wastewater (sinks and basins). IB is most likely internal branch. 4"T is likely to be a 4" trap which prevents vermin, and 5"No2T may also be a trap.

That may or may mot be a manhole in No 44's garden - it's not marked M/H or similar, but if it is one you should be able to see a cover (unless it's been covered over). Is No 44 the end terrace? If so, is there a road parallel to the gable end with any manhole covers?

When I worked as an engineer I used to request drainage plan records from local authorities and water companies - I suspect you can still order them (at a cost) or you can make an appointment to view them at the relevant offices.

They should be able to use a "cat and mouse" to locate the sewer.

Or a Cat and Jenny ...

I second looking up the nearest manhole.
Your engineer should be able to order sewer/mains drawings from the water company. Some have them on line, but be warned, they may not be accurate.
Otherwise, a Cat and Genny, maybe with a sonde (if plastic piping, unlikely if the original 1935 pipes are still in place) will help.
The guy who has dug the trial pit to 1m deep was probably only doing what he was instructed .
Water diving can be very accurate for alignment of pipes, but not for depth.

You can get cctv inside drainage for a condition report.
Do you want to build an extension or renovate? What would you like to know, the capacity ?

Speak to the local water company and check for any applications for build overs
This is when you build over a man hole

Home Renovation Lesson Learned #1 - don't take anyone's word for it, get a second opinion and then check and double check everything yourself.

The Structural Engineer has come by. Looks at me and the handyman like we're morons wondering why we didn't determine the distance the sewer is from the house by checking the manholes on the other properties before we dug. I look at him and say "You gave me the plans marked with where you wanted the trial pits dug" (please see said plans above). He says "I assumed you wouldn't start digging until you checked the distance of the manhole from the house". HOW THE BLOODY HELL WOULD I KNOW TO CHECK THE DISTANCE OF THE MANHOLES IF HE DIDN'T TELL ME TO CHECK THE DISTANCE OF THE MANHOLES?
I know I'm new at this but he's just trying to save his own butt because he told me specifically where to dig so that he could return to determine how deep to make the foundations. Why would I bloody question him and dig somewhere else when he was so bloody sure about its location the first time. We are now digging a third pit in the garden and I will have to pay for another day of labour.

Home Renovation Lesson Learned #2 - ask mumsnet first.

Home Renovation Lesson Learned #3 - make sure I REALLY want the extension I'm planning. I have a feeling I'll be dealing with cock-wombles aplenty in this process.

Thank you very much everyone for all of your help and suggestions.

Don’t worry - the first site investigation job I did on my own I managed to go through a sewer pipe and the digger driver asked me why I didn’t check the manholes first Lesson learned - trust no one and nothing, and especially not service plans which often manage to omit little things like fibre optic cables. I know of a whole catalogue of disasters that happened (not to me fortunately!) because things weren’t on the plans or were in the wrong place or nobody made the obvious checks

Buteo sounds like we’re in the same line of business. I once managed to cut the power to a large office block in Sheffield. My colleague went through the main gas pipe to a major pharmaceutical factory. None of these services were in the place shown on the utility drgs.

Thanks bikerunski, I thought that the advice to check the manholes was to determine depth. I know now.
We found said manhole and had the sewer found in less than 2 hrs. My guy has been digging since Tuesday afternoon and my garden looks like a WW2 battlefield (where's the crying emoji?).