How to…

Tracing and Avoiding Underground Services, Domestic Properties

Tracing underground services is a profession in itself. But with a bit of effort before any project, you should be able to gain a good insight into what is buried where, and avoid costly and sometimes dangerous mistakes, especially on a small domestic project. That said, most services cannot easily be traced, so you are reliant on a few simple rules. But beware, not everybody who lays services plays by the rules, and things could be – and often are – not where you imagine….!

A few basic principles to remember when trying to locate buried services on a domestic property:

• (Most of the points made below relate to Gas, Water, Electric, BT & Cable TV. They do not cover drainage pipes, though there is a note on these at the very end)
• Most services will run from the Highway to the front of the building.
• However they may also run to the side of the building, and often do.
• They are less likely to run to the back of the building, but there are exceptions… we’ll come to this in a bit
• Most services will tend to be at least 200mm-300mm* under the ground, and if laid properly should often be getting on for more like half a metre.

*The trouble with the 200mm – 300mm scenario is that you are likely to come across them when digging out for a driveway or patio. Cable TV and other communications cables are often laid a lot shallower, we’ll come to them in a bit. And beware, any service including even gas or electric could be just under the surface. Nothing surprises us nowadays!

If you do damage underground services, you’re likely to get charged for repair by those who own the damaged service. This is the case for all services with the exception of water. If you damage a water pipe on private property, this is your responsibility to fix, as a private pipe. The relevant Water Authority will not attend to fix this even if you offer to pay them to.

If you damage a gas pipe or electric cable, costs can be quite high. There is no fixed cost for a repair, you will be charged the sum of all of their costs, which can often be getting on for £1,000 gas or electric. BT and Cable TV are often a lot cheaper.

When digging in an area where there may be buried services (nearly everywhere) we strongly recommend that if you are using a digger, always use buckets without teeth. If your digger buckets have teeth on, then those underground services don’t stand a chance! The teeth are further into the ground than the rest of the bucket, out of your sight, and wreaking havoc on anything that may be lurking underneath. And if you do hit something it’s going to cost you.

The majority of our digger buckets have blades on for this reason, as opposed to teeth. Make sure you ask for bladed buckets when you order your digger (click here for digger hire).One misconception about digger buckets and teeth vs blades is that you need teeth on a bucket in hard ground. This is not correct. If your digger is struggling it is not because you don’t have teeth on your bucket, it is because you don’t have the right-sized digger. If you are using a 1.5t mini digger and it’s struggling, you need a 3t digger, and if your 3t digger is struggling, you need a 6t digger, and so on!

Although you will normally need a digger for whatever work you are doing, you should also adopt ‘safe digging practices’, when digging near to buried services, and this includes hand-digging where necessary. (If you want to become an expert in ‘safe digging practices’  then Google ‘HSG47’, this is a 40-page document put together by HSE on the subject.) You are so much less likely to damage a service with a spade than with a digger, especially if you are digging carefully. You should always be doing a mixture of both, a bit of careful scraping away with the digger bucket (with blade not teeth), followed by a bit of careful hand digging by a second person, and then some more careful scraping with the digger. If you see the experts digging holes in the road, you never have one man ploughing on with a digger non-stop, it’s always a mixture of one man carefully scraping with the digger and another watching him dig, and regularly jumping into the hole to have a scrape about.

The man who is watching the digger driver will often be the more experienced of the two, believe it or not. It’s not a job that anybody can just turn their hand to. The more experience somebody has, the more likely they are to spot the tell-tale signs of a buried service further down. These include:

Changes in the ground – if you are digging in clay and you see a vertical strip of stone or different coloured fill, this could have been laid on top of a service. Turn the digger off and jump in with your spade for a poke about

Sand surround – most services should be covered with a surround of some sort, often sand. If you see sand, then again, turn that digger off and get your spade out!

Warning tape – plastic warning tape is incredibly handy nowadays and is often used to cover services, and should ideally be laid a few inches above the service. But be warned – it will often be laid directly on top of the service, giving you little or no warning of the danger just below.

Line of bricks – old electric cables in particular are often covered with a line of bricks, sometimes with markings engraved on 

Concrete protection – this is a bit more tricky. The concrete covers the service to protect it, but if you break it by mechanical means, you may damage the service underneath. Try to dig a hole adjacent to the concrete protection and dig a hole horizontally to identify what is underneath, if anything.

Ground level tell-tale signs – things such as manhole covers, meter boxes, small metal lids, and marker posts, these are all things you should be looking out for, and a lot of covered in depth below. 

Different types of services:

BT
 

BT will often be laid very shallow, more like the 200mm – 300mm quoted above, but sometimes deeper. BT cables may be laid in the ground with no protection, though sometimes they are laid in a duct, particularly on newer properties. Where they are laid in a duct, and where that duct is grey (technically known as BT duct 56, and about 2” in size) then that duct will be very strong, and in comparison to other types of duct, BT ‘duct 56’ is near-indestructible! But be careful around these ducts still – if you have teeth on your bucket and you are digging at ’90 degrees’ to it, then it won’t stand a chance.

If you can find a small grey ‘bt66b’ junction box at the house  then this will normally indicate where the cable goes into the house. You may sometimes see a duct coming out of the ground here, normally 2” grey duct, or sometimes a cable. But beware – a duct on show underneath the ‘bt66b’ box does not mean there will be a duct all the way to the road. You could still be digging around a very thin BT cable that is not in a duct.

The cable and/or duct that goes to the road from the house will often – but not always – be laid at 90 degrees to the front of the house, and in the direction of the highway. The cable and/or duct will often go into an underground BT manhole/chamber at the road, a couple of examples here. 

These will often be marked ‘GPO’, ‘BT’, or ‘British Telecom’. The cable and/or duct will often run between the bt66b box at the house, and the manhole/chamber at the highway, and sometimes you can lift the manhole cover at the highway to see if there is a cable running where you expect it to. But remember these are all assumptions and you can never be certain.

BT cables however may be ‘above’ in the air, between an overhead telegraph pole and the house, as opposed to being buried underground. In this instance they will be very thin, normally just a few millimetres thick and normally insulated with black plastic. If the overhead cable is thicker though, normally a bit more than 1” in diameter, then it is more likely to be electric. Check the pole where the cable comes from, if it is an ‘electric’ pole it will normally have a yellow warning sign on to that effect. BT poles don’t often have any markings, apart from a number.

If you do damage a BT cable in the ground – or if by some miracle you manage to damage an overhead one – then you will need to contact Openreach for repair, not BT. You should find emergency contact details for Openreach by way of a quick Google Search. If you damage the outer plastic on a BT cable but the telephone is still working in the house, you should still report it as a repair. If you have damaged the outer core then water could seep in over time, and you’re better off having it fixed now whilst you have everything exposed, as opposed to later on when you have laid your block paving on top, or whatever you are doing.

Although technically it is possible to detect BT cables, it’s a specialist job which will be beyond the expertise of most people, and not normally possible with equipment available at most hire centres

Water
 

Water pipes come in a variety of different materials. Newer water pipes will normally be blue plastic (technically ‘MDPE’) and will vary from 20mm to 32mm in diameter normally on a domestic property. Older pipes may be a variety of different types of metal, including lead.

On most domestic properties old and new, you will normally find a water meter at the Highway somewhere, normally in the pavement or in a grass verge, which will normally be marked ‘water’. You won’t often find them in the road.

You won’t normally find a tell-tale sign at the house as to where the water goes into the property. However, you should normally have a stop tap just above ground floor level inside the house where the water comes in, and this will often be under the kitchen sink, or in a utility room. Although as we keep saying – nothing is certain – the water pipe will normally run in a fairly straight line from this point to the water meter in the highway.

New water pipes should normally be laid at ‘750mm cover’ under current regs, but they are often laid a lot shallower unfortunately.

Remember if you damage a water pipe, it is ‘your’ responsibility to fix it. You’ll have to turn it off at the water meter first. If you can’t find a water meter then you’ll have to ‘squeeze it off’ in the direction from where it’s running, normally the highway. You can do this with a ‘squeeze’ (for MDPE pipe), but you’ll struggle to get one of these in a hurry from the local builders’ merchant.

Every builder and groundworker should own one, in our opinion, you never know when you may need one in a hurry. If you need to stop the flow in a hurry, and you don’t have a ‘squeeze’ then for an MDPE pipe you can normally bend it over on itself if you have enough showing, to stop the flow. Put some tape around it to hold in bent back, or use a cable tie.

To fix an MDPE pipe, you’ll need to expose a decent length of the pipe, ideally about 700-800mm at least. Cut out about 500mm of the damaged pipe and make a repair with a new short length of pipe and a couple of compression fittings.

Make sure you buy ‘inserts’ as well, these inserts simply push into the pipe before you push the compression fitting onto it. Unfortunately, you can’t normally buy a short length of pipe from the merchants, you’ll be buying a 25 metre roll at least. Do the fittings up with a set of ‘stilson’ pliers or a monkey wrench. It isn’t good enough to do them up hand-tight, they will leak later on. Most builders merchants will be familiar with the types of fittings required to fix a water pipe. If you are in any doubt or you don’t fancy tackling it yourself, a plumber will normally be familiar with these underground pipes and how to fix them.

For damaged water pipes made of various metals including lead, fittings are a lot less common, and to make matters worse you are normally going to need them in a hurry. A lot of builders’ merchants do sell them or try a plumbers’ merchant if not. For non-MDPE pipes, you are more likely to need a plumber to do the repair if you’re not competent enough yourself.   

Electric
 

Now we’re getting onto the dangerous stuff. Obviously electricity can kill, and underground electric cables can burn you. It doesn’t help that you’re digging with digger buckets and spades that are made of metal. You can buy digging spades that are insulated with plastic, but they only reduce the chances of shock. And you can still suffer bad burns from electric cables. And just because it’s ‘only a feed to the house’, doesn’t mean to say that you won’t get a nasty shock from it. Larger cables in the Highway will often ‘trip out’ if you damage them, especially if they are close to a sub-station, but smaller cables in the garden of a domestic property will not normally trip out.

There are rarely tell-tale signs as to where an electric cable originates at the Highway. They often start at buried joints in the path or verge, in the road and often on the other side of the road.

There are clues though as to where they terminate at the house. You should normally find an electric meter box at the house, and more often than not, on the side of the house.

 The electric feed to the house will normally come into the bottom of the meter through a plastic duct. Beware though, where the white or black duct goes into the ground, the cable will often continue to the Highway as a buried cable, not in a duct. Where it is laid in a duct, the duct will normally be black and about 2” in diameter. Watch out though – BT cables are often laid in black duct as well, just to confuse you!

Electric cables and ducts should ideally be laid at about 450mm cover, but they will often be a lot shallower. Cables may also be laid in metal ducts or conduits, but in this case they will be difficult to differentiate from metal gas pipes and metal water pipes.

There is some good news with electric though – you can often trace it. You’ll need a CAT. (stands for Cable Avoidance Tool) and although relatively simple to use, we do recommend a basic understanding of them, head to Youtube where you’ll find plenty of tutorials.

And although expensive to own, you should be able to hire one from most tool hire shops and some builders’ merchants. When you do trace any services such as electric, always mark them up with spray paint and always put a line either side of where you think you have traced the service, to give yourself a bit of a buffer either side. And of course, still proceed with caution…! 

Some electric cables will be overhead, and will go from an electric pole (normally in the Highway) to the outside of the house higher up. An electric pole will normally have a marking on the side, normally a yellow sign which says ‘Danger Electric’ or similar. If there are no markings on it, then the pole is more likely to be a BT Telegraph pole, which will mean that the electric is still likely to be buried underground.

If you do damage a buried electric cable:

Stay away from the damage, and make sure others do as well.

Turn off any plant and machinery and move away. If there is a chance that the digger bucket is still in contact with the damaged cable, beware of touching any metal parts of the digger including grab handles as you exit the machine.

Telephone the relevant provider immediately. At the time of writing, Northamptonshire is covered by Western Power Distribution, but contracts are regularly awarded to different companies. A quick Google search should tell you whom to ring.

Gas
 

As with electric, this is one of the more dangerous services to be digging around. And as with electric, you won’t often find a tell-tale sign as to where the pipe comes from in the highway.

At the house though, you will often find a meter box similar in appearance to an electric meter box.

You should see a white duct going vertically from the meter box into the ground, after which a gas pipe will normally be buried in the ground without the protection of a duct.

As a lot of gas pipes are ‘moled’, so you won’t often have any sand surround or warning tape, and the depth of the pipes is anybody’s guess unfortunately. Where gas pipes are moled, they will normally be yellow plastic (MDPE) and will normally range from 20mm to 32mm diameter. Older gas pipes will be metal, but will often look the same as an electric duct or conduit, or a metal water pipe. Quite often when MDPE gas pipes are moled, these will replace an older metal pipe. So you may think you have found the gas pipe, when it may only be one of two, one of which will be redundant. Treat anything you find as live!

Gas pipes cannot easily be traced, especially the plastic MDPE ones. If you dig a hole at the base of the gas meter box, you should be able to ascertain the direction of the gas pipe towards the highway, and it may benefit you to dig further trial holes (by hand) towards the highway to help identify its path.

If you damage a gas pipe, stay away from it and obviously do not attempt to repair it. Even if you were able to get hold of the fittings required for repair, it’s not as simple as just fixing the pipe, a gas pipe repair will often require an engineer to go into the house to check the feed to the boiler.

If you have external meter boxes, namely for gas and electric, then these services will nearly always run to these. And these will often be on the side of the house, the services will normally come from the road, square to the house and in line with the meter box, though of course they could have been laid in any fashion. And often are!

Frequently Asked Questions (and some silly ones)