When you are repairing a broken piece of pipe, cut out the broken section and dispose of that. Now what you need to do is get a new section of pipe into the system. The problem with a lot of pipe systems is that the two pipes on either side of the broken section are fixed in place – they might even be concreted in.
If you were using ordinary sockets to put in a new piece of pipe, you could glue a socket on the end of the pipe on the left and the end of the pipe on the right. However, you would have to get enough pipe movement to pull the pipe out of the way for the new piece to fit into the sockets. The other problem with using sockets is, if the pipe system is in a process line, you have to glue the sockets on. Depending on what pressure you are operating on, ideally, you will have to wait 12 to 24 hours before you can get the system back into operation again.
The problem of restricted movement can be overcome by using unions. If you use a union on the two ends of the cut pipe, you can unscrew the union, put it on the new piece of pipe on one side, and unscrew the other union, and put it on the other side of the new pipe. You can then slot the new piece of pipe straight in and tighten up the unions. If you do choose to use unions, you have to make sure that your measurements are extremely accurate, especially if there's no movement at all in the pipes. This is because it is important that when you tighten the unions, the EDPM O-ring inside the unions makes a seal. Remember, you would still need to glue the unions onto the pipe, meaning that you would still have to wait for that glue to set before you could re-pressurise the system.
Another option, if you were running a low-pressure system, is to use EPDM couplers. They simply slide on either side, then you can put the new piece of pipe in the gap and the couplers can be slid back over the top where you would tighten up the O-rings. This is a very quick fix, but you would be limited with pressure. For the smaller fittings, they only operate at about 0.5 to 0.6 bar pressure, which is the equivalent of 5m/6m of head water. For fittings 65mm and larger, we supply a rubber coupling which has extra reinforcement steel around it, and will take up to 2 ½ bar – equal to 25m of pressure – which is probably more than the majority use in their systems.
The king of all fittings, in our opinion, is a compression coupling. This has a thick O-ring inside – more of a flat ring really – which sits against the seal. When tightening the union, it compresses that flat seal inside and compresses it down onto the pipe. Compression couplings are excellent because they slide onto the pipe, just like the rubber couplings, and then they will slide down the pipe onto the new piece of pipe in the middle. To get them onto the pipe, you need to remove the O-ring, slide the union up, then place the O-ring on and slide it up. You can use some lubricants to make it easier – if it's not a WRAS approved application you can maybe use fairy liquid, or there are some WRAS approved lubricants you can use that just help slide it up and back down the pipe and won't affect the seal. These fittings are also great because they will take up to 10 bar pressure. Once you have put in your new piece of pipe using the compression couplings, your system will be ready to go straight away, and you can put it up to 10 bar immediately.
- Sockets are the easiest and cheapest option, but you need to have movement in the pipe and you need to wait before you can get your system running again.
- Unions overcome the issue of movement in the pipe, but they do not overcome the waiting time.
- Rubber couplings overcome the issue of movement in the pipe and the waiting time, so you can get your system back up and running quickly, but there are pressure limitations.
- Compression couplings overcome the movement of the pipe, the waiting time, and the pressure limitations, making them the most effective, depending on your system.