FTTP Install Question - Can I preinstall the internal fibre?

My brother has a small business that has an existing BT Business FTTP installation. He is having a rear extension built and the FTTP installation will need to be moved/rerouted ....basically reinstalled completely. Thats if the buider doesnt destroy it first. But crucially the data cabinet, where the ONT is currently, is in the middle if the building and a good distance from where Openreach will want to install any external box to splice the external/internal fibres together.

Questions
Is there any possibility that Openreach will give you an length of internal fibre cable so that it could run into the required area before the building works finish? i.e. when ceilings are down

Or alternatively could I possibly acquire one off a friendly Openreach engineer pre install date?

I wasnt sure if anyone had any experience of this ? I appreciate its not usual but it makes sense to me..

Thanks Mark

Ask BT to come and move the fibre to the correct / new location. This will be chargeable.

At the appointment ask the Openreach engineer to only 'first fix' the internal cable loosely to where you want it. Explain what is happening with the drop ceilings etc. Make sure there is sufficient slack left.

Once the install has been re-tested, Keep the ONT connected to the end of the fibre and carefully seal it in a plastic bag and protect it from damage. Very carefully coil up the fibre cable in a loop around 300mm in diameter and secure with some electrical tape. Keep the ONT bagged up and sealed. Remove the power plug and store for safe keeping..

Explain to the site manager that this is fibre cable and can be very easily damaged, and should be kept somewhere where its not going to be trampled by all the trades (ideally in a sturdy cardboard box).

Once the main first fix timber work, joinery, plasterwork etc is done - un-real the cable to the correct place and test the ONT before any voids etc are closed up.

It is not really clear that the ONT would need to be relocated, or whether it would be better to move the data cabinet etc. But let us assume that the ONT must be relocated and the data cabinet would stay where it is. In that case, the best thing to do would be to accept the ONT in the new position and run from the ONT to the data cabinet with a new length of CAT 6 cable, rather than do some dodgy job with a length of fibre from ebay.

If, as I assume, the new extension has some data points too, then the cable to the ONT is just more of the same.

When I had fttp installed, I knew it could not be in the final location I wanted for the router. I did consider getting a fibre extension kit. But in the end, I just did a CAT 6 cable from ONT to router and don't regret it.

Thanks for the reply ...unfortunately the new fibre installation probably needs to take a different path through the building from the existing install.

The existing ONT is in the centre of the building next to the data cabinet and really needs to stay there.

If I managed to acquire a length of Openreach internal fibre cable ...do you think that the install engineer would be prepared to use?

id probably run cat6 to somewhere near where the external joint box is going to be just in case the engineer just wants to dump the ONT there ....

Where is the existing splice point (CSP) in relation to the ONT - does the CSP have to move or is it just the route the fibre cable will have to take.

I understand that the ONT location will basically not move. Its really just the revised internal fibre cable route, correct?

Thanks for the reply.

Id like to keep the ONT where it is next to the data cabinet ...its safer.

But as you say running cat6 to a potential alternative location for the ONT (i.e. easiest for the engineer) would be wise.

Running the fibre up front just seems sensible if only it was available and the engineer was likely to use it after you ran it for him.

In reply to a post by pekoz1:

Running the fibre up front just seems sensible if only it was available and the engineer was likely to use it after you ran it for him.

The alternative is for your builder to install a cable pathway that the engineer could use.

This typically is an appropriately sized flexible conduit (20mm or 25mm dia. iis fine) with a decent draw wire/rope/string installed. On install the engineer pull the fibre cable back along the conduit to where it needs to exit to meet the CSP.

Is the CSP the external junction box where they splice the external and internal fibre together?

Also on the ONT is there a premade end on the internal cable?

Thanks

Yes for both.

Thanks

Hi,

In reply to a post by Pheasant:

In reply to a post by pekoz1:

Running the fibre up front just seems sensible if only it was available and the engineer was likely to use it after you ran it for him.

The alternative is for your builder to install a cable pathway that the engineer could use.

This typically is an appropriately sized flexible conduit (20mm or 25mm dia. iis fine) with a decent draw wire/rope/string installed. On install the engineer pull the fibre cable back along the conduit to where it needs to exit to meet the CSP.

This is probably the easiest approach. Black 25mm water pipe, all the way from the building entry to the ONT location without any kinks or joints is a good choice - easy to pull a fibre through that.

Smooth bore conduit like twin-wall is a good choice.

The inside-out FTTP cable that Openreach use is actually very light and narrow (around 3mm OD) so even regular flexible conduit (aka Kopex) is generally fine as long as:
1. The run isn't massive (add regularly spaced and accessible inspection boxes if so)
2. Any bends are kept gentle and aren't too tight; and
3. Conduit is adequately secured in voids (use saddles or p-clips), so it doesn't bunch up when cable is being pulled through

Edited by Pheasant (Wed 30-Sep-26 10:44:05)

Hi,

That is why, for the inexperienced 25mm alkathene pipe is great. No issue with bunching, it'll be fine even if only secured haphazardly and (unless you kink it) you will never get a tight enough bend radius to cause any problems pulling stuff through.

Don't get me wrong I like your inventiveness (you don't happen to be a farmer by any chance! 😅) but personally I'm not really a fan of putting services through what amounts to (from external appearances) water pipe.

I know it's done, and I have plenty of evidence from farming acquaintances that think alkathene (HDPE) is the best thing ever. But I just can't bring myself to recommend using it for this. Especially indoors.

It's also an absolute barsteward of a thing to wrestle into place, at the best of times, let alone indoors.

I would certainly recommend against blue pipe but black is sufficiently meaningless as a colour that I don't see an issue.

I agree it is a pain to manoeuvre but that stiffness forces an installation such that it is easy to pull fibre through.

I used 25mm white electrical conduit, in retrospect, 20mm would have been fine. I used normal inspection bends.

You can get White 22mm Polybutylene water pipe, but quite expensive compared to 20 mm conduit, but it can be curved. £121.89p from Screwfix for 25 metres. Plus other options including 28mm.
I have not used the above, as stated I used PVC conduit with a total of six bends

Cheers!

Indeed Clive, rigid electrical conduit is going to be the Rolls Royce solution here (or anywhere) - it's just the costliest to supply and install, is all. Then again if the sparky is already on site...