Cast Iron Outlet Tees and Saddle Branches to Drawing

Adding a service connection to a main that is already in the ground is a different problem from building a tee into a new line. You cannot cut the pipe in half, you cannot get a machine around it, and whatever you bolt on has to seal against a surface that has been buried for thirty years. That is what an outlet tee is for.

What an Outlet Tee Does That a Standard Tee Cannot

A standard tee replaces a section of pipe and joins three runs at a fixed geometry. An outlet tee clamps onto the outside of an existing main and adds a branch through a hole cut in the pipe wall. The main keeps running, the excavation stays small, and the connection is made in an hour rather than a day.

The trade-off is that all the sealing has to happen on the outside diameter of an old pipe, which is rarely round and rarely clean. That constraint shapes the whole design: the saddle has to conform, the gasket has to be generous, and the branch has to be strong enough to carry the load that the main no longer carries around the opening.

Saddle Radius: the Fit That Decides Whether It Seals

The saddle is the curved underside of the fitting that sits against the pipe. Its radius has to match the pipe's outside diameter closely enough that the gasket is compressed evenly all the way around.

A saddle that is 1 mm too small contacts on two lines and leaves a gap at the sides. A saddle that is 1 mm too large rocks and compresses the gasket at one point. Both leak.

Real pipe is not nominal. A ductile iron main is within tolerance, but a cast iron or steel main that has been in the ground can be pitted, out of round, or covered in scale. That is why most designs use a thick rubber gasket, 6 to 10 mm, that can absorb 2 to 3 mm of irregularity.

We cast the saddle radius to the pipe's nominal outside diameter and hold it to plus or minus 0.5 mm. If you are working on old pipe, measure the actual diameter at the connection point and tell us; a slightly different radius is a pattern change, not a redesign.

Branch Sizes and the Reinforcement Around the Opening

Cutting a hole in a pressurised pipe removes the wall that was carrying the hoop stress, and the fitting has to put that strength back. Two mechanisms do it: the saddle body itself, which wraps around the pipe, and the branch neck, which has to be thick enough to resist the bending that the branch load imposes.

As a rule, a branch up to about one third of the main diameter needs no special reinforcement beyond a properly designed saddle. Above that, the fitting needs a longer body or a reinforcing pad, and the design should come from a pressure vessel calculation rather than from a catalogue.

We cast the branch neck thicker than the mating pipe requires, because the neck is where the bending moment from the service line lands.

Bolted, Clamped or Cast-In

A bolted outlet tee uses two or four bolts through the saddle flanges to compress the gasket. It is the most common design, it can be removed, and it is the one that works on the widest range of pipe conditions.

A clamped version uses a band or a strap around the pipe instead of bolts through the body. It fits where there is no room for a bolt head, but the clamp force is less predictable.

A cast-in outlet is welded or cast onto a new pipe at the factory and is not a field connection at all. It gives the best seal and the lowest profile, and it requires the pipe to be made with it.

Most of our work is the bolted type, in ductile iron, with a nitrile or EPDM gasket depending on the fluid.

Working on a Live Main: Clearance and Access

The fitting has to be installed by a crew with a spanner, in a trench, often with water in the bottom. That reality should drive the design.

Bolt heads need clearance for a socket rather than only a spanner, and they should all be on the same side so the fitter is not climbing around the pipe. The branch outlet should be long enough to get a coupling onto it without the coupling fouling the main. And the whole assembly should be liftable by two people, which caps the weight at around 40 kg for a cast iron body.

Where the trench is tight, a two-piece saddle that assembles around the pipe is easier than a one-piece body that has to be slid on from the end.

Coating Inside and Out

The outside of an outlet tee is buried and the inside is in contact with drinking water, so it needs two different coatings.

Outside: a zinc-rich primer plus a bitumen or epoxy topcoat, at 200 to 300 micrometres. The critical area is the gap between the saddle and the pipe, which is where water sits and where the coating is hardest to apply.

Inside: epoxy at 250 to 400 micrometres, because a cement lining cannot be applied to a shape this small and complex. The coating has to be pinhole-free; a holiday in a potable water lining is a corrosion cell and a contamination risk.

We spark test the lining on potable water fittings rather than relying on a visual check.

Pressure Testing a Branch Connection

A fitting is tested in the factory, but the joint is tested on site, and the factory test only proves the casting.

The factory test is a hydrostatic test of the body at 1.5 times the rated pressure, held for the standard's duration. That finds porosity and casting defects.

The site test is the one that matters for the connection, and it depends on the gasket seating properly against a pipe surface nobody inspected. That is why the installation instructions matter as much as the fitting: clean the pipe, check for scale, position the gasket, torque in sequence.

We supply a torque figure and a sequence with every batch, because most joint failures are installation failures and a torque wrench costs less than a repair excavation.

Tapping a Live Main: the Sequence

An outlet tee on a live main is installed in a fixed sequence, and each step depends on the one before.

The pipe surface is cleaned and measured. The saddle is fitted with the gasket and the bolts are torqued in sequence. The valve is bolted to the branch. The tapping machine is mounted on the valve, the cutter passes through the open valve, the hole is cut, the coupon is retrieved, and the valve is closed.

Each step has a failure mode. A dirty pipe surface leaks at the gasket. An untorqued bolt sequence leaves the saddle cocked. A valve that is not fully open stops the cutter. A coupon that is not retrieved sits in the main and blocks a downstream valve.

What the foundry controls is the saddle radius, the branch bore and the flatness of the mating faces. What the crew controls is everything else, which is why we supply the torque figure and the sequence rather than assuming they are known.

Reference Price Range and Minimum Order

Reference price range: US$0.10 to 100.00 per piece, FOB Qingdao. Minimum order quantity: 500 pieces per item. The final unit price is quoted against your drawing and depends on part weight, material grade, moulding process, machining allowance and tooling amortisation. Reference prices are valid until 31 December 2027.

Frequently Asked Questions

Can the outlet tee be installed without shutting off the main?

With a tapping machine, yes. The fitting is bolted on, the valve is attached, and the hole is cut through the valve under pressure. We supply the fitting; the tapping equipment comes from a specialist.

What pipe materials can the saddle fit?

Ductile iron, cast iron, steel and asbestos cement, each with a different gasket and radius. Tell us the pipe material and outside diameter at order.

How much out-of-round can the pipe be?

Up to about 2 percent of diameter with a thick gasket. Beyond that the saddle will not seat and a different connection method is needed.

What is the maximum branch size?

About one third of the main diameter without reinforcement, larger with a designed body. We will confirm against your main size.

Is the branch threaded or flanged?

Both are available. Flanged is standard for DN50 and above; threaded is common for small service connections.

Do you supply the gasket and bolts?

Yes, as a matched set, because the gasket hardness and the bolt grade are part of the joint design.