Intro
On many jobs, you can’t shut the building down. Tenants need water. Shops must stay open. Secure shut-off valve installation without stopping water flow is possible and safe if you use the right method. In this guide, you’ll learn three proven approaches: pipe freezing, PEX pinch-off, and under-pressure tapping. We’ll cover tools, steps, and checks. You’ll see where each method fits, the time it takes, and the risks. Keep it simple. Work clean. Finish fast. That’s the goal.
Quick Answer
Yes, you can install a shut-off valve on a live line without shutting water. Use pipe freezing (for copper/steel), a PEX pinch-off tool (for PEX), or an under-pressure tapping kit with an integral valve (for adding a new branch). Each method is secure when you follow ratings, steps, and safety rules.
Table of Contents
Key Takeaways
- Three secure options: freezing, PEX pinch-off, or under-pressure tapping.
- Typical hold times: 30–60 minutes for freezes; 15–45 minutes for PEX pinch-offs.
- Common sizes: 15 mm, 22 mm, 28 mm, and 1/2"–3/4" lines.
- Work within ratings: usually 3–5 bar mains, up to 10 bar max (check kit).
- Plan a backup: a second freeze head, a second pinch, or a nearby drain.
Why Work Under Pressure
Sometimes you can’t isolate. The main stopcock is seized. The building shut-off is shared. Or the job is in a live shop with strict hours. Secure shut-off valve installation without stopping water flow keeps the site open and your job on schedule. It also avoids drain-down and refill time. On most small jobs, this saves 1–2 hours. On big sites, it can save a whole day.
When you choose the right method, you keep control. You also cut risk. You add a valve where you need it, not only where you can isolate. That’s good planning and good service.
Before you start, check these basics.
- Know your pipe: copper, steel, PEX, or CPVC. Measure OD: 15 mm, 22 mm, 28 mm, or 1/2"–3/4".
- Check pressure: many buildings run 3–5 bar. Some pumps push 6–8 bar.
- Check temperature: freezes work best below 20°C water. Hot lines reduce hold time.
- Choose the valve: full-bore ball valve, WRAS-approved. Press-fit or compression for wet work. Push-fit rated for 10 bar cold if used.
- Safety: eye protection, gloves, CO2 safety for freeze kits, battery care for power tools.
- Backup plan: second freeze head, second pinch, nearby drain, or extra repair clamp.
- Communication: tell the client the plan, the hold time, and the small risk of thaw.
Tip: For quotes and clear scope, tools like Donizo help you capture site notes (voice, text, photos) and turn them into a clean proposal with e‑signature. That reduces questions on the day.
Method 1: Pipe Freezing (Copper/Steel)
Secure shut-off valve installation without stopping water flow is most common with an ice plug. You freeze the pipe, make the cut, fit the valve, and thaw.
When to Use
- Copper or steel lines, 15–28 mm.
- Straight runs with at least 150–300 mm of working space.
- Cold or ambient water (below 20°C preferred).
What You Need
- Electric freeze clamp or CO2 freeze kit (rated up to 10 bar, check spec).
- Thermometer or infrared gun (optional but useful).
- Mini cutter or cordless pipe saw.
- Press tool or spanners for compression fittings.
- Full-bore ball valve (15 mm/22 mm/28 mm or 1/2"–3/4").
Steps
- Identify freeze point 200–300 mm upstream of your cut.
- Wrap or clamp the freeze head. Ensure full contact, no paint lumps.
- Start the freeze. With CO2, follow canister instructions. Typical plug forms in 5–10 minutes on 15 mm, 10–15 minutes on 22 mm.
- Confirm the freeze: open a basin tap downstream. Flow should drop to drips.
- Mark and cut out a 20–40 mm section for your valve body.
- Deburr and clean the pipe ends. Keep swarf out of the line.
- Fit the valve using press-fit or compression. Tighten evenly. For press, use correct jaws (M/V profile) and check the witness marks.
- Slowly warm the freeze head or let it thaw naturally. Watch for leaks as pressure returns.
- Operate the valve fully open/closed 2–3 times. Check joints at 2, 5, and 15 minutes.
Notes
- Have a tray and towels ready. Expect 100–300 ml of water on cutting.
- For 28 mm, allow more freeze time (15–20 minutes). Always follow the kit chart.
- Don’t freeze on soldered joints. Freeze 100 mm away from fittings.
Method 2: PEX Pinch-Off and Valve Install
For PEX, a pinch-off tool is fast and clean. It compresses the tube to stop flow. Then you cut and add the valve.
When to Use
- PEX lines, 16–25 mm or 1/2"–3/4".
- Accessible straight runs with good support.
What You Need
- Rated PEX pinch-off tool (check maker’s max time, often 30–45 minutes).
- Ratcheting cutter.
- PEX ball valve or brass ball valve with PEX adapters (crimp/press/push-fit).
- Crimp rings/sleeves and tool, or press sleeves, as required.
Steps
- Place the pinch tool 150–200 mm upstream of the cut. Centre it and close fully.
- Confirm stop: open a downstream tap. Flow should stop.
- Cut out a 20–40 mm section for the valve.
- Slide on rings or sleeves. Insert the valve. Keep full insertion depth (usually 19–23 mm on 1/2").
- Crimp or press to spec. Check go/no-go gauge if crimping.
- Release the pinch slowly. Watch joints for 2–5 minutes.
- Operate the valve open/closed. Check again at 15 minutes.
Notes
- Do not exceed the tool’s max pinch time.
- Don’t pinch within 10–15 pipe diameters of a fitting.
- Some PEX brands allow up to 3 pinch events per spot; check the brand sheet.
Method 3: Under-Pressure Tapping With Valve
If you need a new branch with its own isolation, use an under-pressure (hot/wet) tap. You install a saddle/tee and a valve, drill through the live main, then close the valve. Flow in the main keeps going.
When to Use
- Adding a branch without shutting the main.
- Copper, ductile iron, or steel mains. Some systems also support PVC/PE with proper saddles.
What You Need
- Under-pressure tapping kit with valve and drill adapter.
- Tapping saddle or mechanical tee sized for your main (e.g., 22 × 15 mm, 28 × 22 mm).
- Full-bore ball valve rated for mains pressure (10 bar common).
- Cutting bit for the pipe material.
Steps
- Clean the main. Fit the tapping saddle or mechanical tee. Torque to maker spec.
- Mount the valve onto the outlet. Ensure gasket alignment.
- Attach the tapping drill through the open valve.
- Drill the main under pressure. Keep steady feed. Collect coupon if designed.
- Retract the drill fully. Close the valve. Remove the drill.
- Pressure test the saddle and valve. Then connect your branch.
Notes
- Use WRAS-approved parts. Avoid self-piercing saddle valves; many codes don’t allow them on potable lines.
- Common branch sizes are 15 mm and 22 mm. Follow the maker’s pressure and temperature limits.
Quality, Safety, and Code Notes
- Always use full-bore ball valves for isolation. They give reliable shut-off and low restriction.
- Check local code. In general, self-piercing saddle valves are not allowed for permanent work.
- Don’t mix metals without isolation (e.g., copper to galvanised). Use a dielectric fitting.
- Freezing near hot water lines is risky. Above 40°C, freeze time rises, and hold time drops.
- Wear eye protection. Live work can spit under pressure.
- Tag and test. After install, cycle the valve and label it.
This pairs well with understanding professional proposals and project timelines so clients know what to expect during live work.
Time, Pricing, and Client Communication
- Typical time on site: 30–60 minutes for PEX pinch-off; 45–90 minutes for a freeze and valve; 60–120 minutes for under-pressure tapping.
- Allow extra 15–20 minutes for checks.
- Price the risk and the kit cost. Many contractors add a live-work fee line.
For fast approvals, platforms such as Donizo let you create branded proposals, send a client portal link, capture e‑signatures, and convert to an invoice in one click. This reduces back‑and‑forth and gets you on site sooner. It also works well with invoice templates that save time.
Common Mistakes to Avoid
- Rushing the freeze: cut only after you confirm flow is stopped.
- Using the wrong valve type: avoid gate valves; use full-bore ball valves.
- Skipping deburr and clean: burrs damage O‑rings in press/push fittings.
- No backup plan: always have a second stop method ready.
- Ignoring support: add clips within 300–500 mm of a new valve to prevent strain.
FAQ
Can I install a shut-off valve without turning water off?
Yes. Use pipe freezing for copper/steel, a rated PEX pinch-off tool for PEX, or an under-pressure tapping kit with an integral valve to add a new branch. These are standard methods when the main cannot be isolated.
How long does an ice plug hold during pipe freezing?
Commonly, 30–60 minutes on 15–22 mm lines if water is near room temperature and the kit is used correctly. Larger pipes take longer to freeze and may hold for a shorter window. Always follow the freeze kit chart and keep a backup ready.
What valve is best for live installs?
A full-bore ball valve, WRAS-approved, with press-fit or compression ends. For PEX, use a PEX-compatible ball valve with the correct crimp or press sleeves. Push-fit can work if it’s rated for 10 bar cold and the maker allows wet installs.
Is under-pressure tapping safe in buildings?
Yes, when you use the right saddle/tee, a rated valve, and a proper tapping kit. It’s a common method to add a valved branch (15 mm or 22 mm) to a live main. Avoid self-piercing saddle valves unless a local code specifically allows them.
What about pressure and temperature limits?
Most building supplies run 3–5 bar. Many fittings are rated up to 10 bar cold. Freezing works best below 20°C water. For hot lines or higher pressures, use a professional line-stop service or plan a shutdown.
Conclusion
Secure shut-off valve installation without stopping water flow is practical and safe. Choose the method that fits your pipe and space: freeze for copper/steel, pinch-off for PEX, or an under-pressure tap for new branches. Next steps: 1) Assess pipe, pressure, and access. 2) Pick the right rated kit and valve. 3) Plan a backup stop. For faster approvals and clean scope notes, tools like Donizo help you send clear proposals and capture e‑signatures fast. Do it once. Do it right. Keep the water on and the job moving.
