If you run a large building, the heating and chilled water systems behind the scenes are doing a lot of work. They keep offices warm in winter, keep server rooms cool all year, and keep people comfortable without anyone really noticing. So when you need to add a new connection to one of these systems, the last thing you want is to drain the whole circuit and shut everything down.
This is where hot tapping pipework comes in. It is a way of adding a new branch to a pipe that is still full and still running, with no need to switch the system off.
What heating and chilled water systems are
In most large buildings, heating and chilled water move around in closed loops. A boiler or heat source warms the water for heating. A chiller cools the water for air conditioning. The water then travels through pipes to radiators, fan coil units, air handling units and other equipment, before returning to be heated or cooled again.
Because these loops are sealed and treated with chemicals to stop rust and scale, draining them is a real hassle. You lose the treated water, you have to refill and re-treat the system, and you often have to bleed out trapped air afterwards. That can take days, not hours.
Why a shutdown is such a problem
For building services and estates teams, downtime is expensive and disruptive. A few examples:
- In a hospital, you cannot simply turn off the heating to a ward.
- In a data centre, the chilled water keeps the servers from overheating, so a shutdown is a serious risk.
- In an office or shopping centre, a cold or stuffy building means unhappy people and lost business.
So when a new connection is needed, perhaps for a new air handling unit or an extra zone of heating, draining the whole system is rarely a good option.
How hot tapping works on a live system
Hot tapping lets you make a new branch on a pipe while the water is still flowing inside it. The basic steps look like this:
- A fitting is fixed to the outside of the live pipe, usually by welding or bolting.
- A valve is attached to that fitting.
- A special cutting tool passes through the open valve and drills a clean hole in the pipe wall.
- The cutter and the cut-out piece of pipe are pulled back out, and the valve is closed.
- The new branch pipework is then connected to the valve.
At no point does the system have to be drained or switched off. The water keeps moving, the building stays warm or cool, and the new connection is ready to use.
Because heating and chilled water can run at different temperatures and pressures, the work must follow strict safety rules. The Health and Safety Executive sets out the duties for keeping pressure systems safe in the Pressure Systems Safety Regulations 2000, and any work on a live system should be planned with these in mind.
Hot tapping compared with draining the system
Here is a simple comparison to show why hot tapping is often the better choice for HVAC pipework.
| Point to consider | Draining the system | Hot tapping |
|---|---|---|
| System shutdown needed | Yes | No |
| Heating or cooling lost during work | Yes | No |
| Treated water lost | Yes | No |
| Refill and re-treatment needed | Yes | No |
| Time on site | Longer | Shorter |
| Disruption to the building | High | Low |
Where hot tapping fits with other pipework
Hot tapping is often part of a wider job. Once the new branch is in place, you may need extra pipe runs, supports and fittings to reach the new equipment. This is where mechanical pipework services come in, joining the new connection neatly into the existing system.
After the work is done, it is good practice to check that the new connection holds firm under working conditions. You can read more about pressure testing after hot tapping to understand how the new branch is checked before the system goes back to full use.
Getting it right on your site
Every heating and chilled water system is a little different. Pipe material, size, temperature and pressure all affect how the work is planned. The key point is that you do not have to choose between a new connection and keeping the building running. With hot tapping pipework, you can have both.
If you are planning a new connection on a live heating or chilled water system, the RDS Pipeline team can talk you through your options. Call 01277 500510 or get in touch through our website to discuss your project.
