HVAC523

Piping and Fittings

Copper tubing

Copper tubing was developed in the 1920s to provide an alternative to iron piping in a variety of uses.

Desirable features

Good pressure and temperature rating for typical hydronic applications.

Good resistance to corrosion from water-based system fluids.

Smooth inner walls that offer low flow resistance

Desirable features

Lighter than steel or iron piping of equivalent size.

Ability to be joined by the well-known technique of soft soldering

Copper pipe size

Copper pipe is available in a wide range of sizes and wall thicknesses.

The type of tubing used in hydronic heating is known as water tube.

In the United States, copper water tube is manufactured according to strict standards.

ASTM B88

This standard is known as ASTM B88.

American Society for Testing and Materials

ASTM B88

According to ASTMB88, the copper water pipe size refers to the nominal inside diameter of the pipe.

The word “nominal” means that the measured inside diameter is approximately equal to the stated pipe size.

Copper tube sizing

The outside diameter of copper water tubing is always 1/8” inch larger than the nominal inside diameter.

For example, the outside diameter (O.D.) of ¾” inch type M copper tubing is .875 inches

This is exactly 7/8” inches, or 1/8” inch larger than the nominal pipe size.

Copper tubing wall thickness

Copper water tube is available in three wall thicknesses designated as type K, L, and M in order of decreasing wall thicknesses.

The outside diameter of K, L and M tubing are identical.

This allows all three types of tubing to be compatible with the same fittings and valves.

Copper M tubing

Because operating pressures of residential and light commercial hydronic heating systems are relatively low, the thinnest wall copper tube (type M) is most often used.

This wall thickness provides several times the pressure rating of other common hydronic system components.

Hard Drawn Tubing

Two common hardness grades of copper water tube are available.

Hard drawn tubing is supplied in straight lengths of 10 and 20 feet.

Because of its straightness and strength, hard drawn tubing is the most commonly used type of copper tubing in hydronic systems.

Hard drawn copper Tubing

Soft Copper Tubing

So-called soft drawn tubing is annealed during manufacturing to allow it to be formed with simple bending tools.

It is useful in situations where awkward angles do not allow proper tubing alignment with standard fittings.

Annealing

In the cases of copper this process is performed by substantially heating the material (generally until glowing) for a while and allowing it to cool. Unlike ferrous metals which must be cooled slowly to anneal, copper can be cooled slowly in air or quickly by quenching in water. In this fashion the metal is softened and prepared for further work such as shaping, stamping, or forming.

Annealed copper tubing

Hard drawn copper tubing support

Horizontal runs of copper hard drawn tubing must be supported at a maximum of every 12’.

Vertical runs of copper hard drawn tubing must be supported at a maximum of every 10’.

Always refer to local code for proper spacing

Hard drawn copper tubing support

These support spacings do not include any allowances for the extra weight of other system components such as circulators or expansion tanks.

When such components are present, the piping should be supported immediately adjacent to the component.

Soft drawn copper tubing support

Copper soft drawn tubing 1 ¼” and smaller on a horizontal run must be supported at a maximum of every 6’.

Copper soft drawn tubing 1 ½”” and larger on a horizontal run must be supported at a maximum of every 10’.

Vertical spacing for all sizes is 10’

Pipe support materials

A number of different supports are available for copper tubing.

Split rings

Bell hanger

J hook Clevis hanger

Adjustable strap

2 hole pipe strap

Copper strap

Two hole plastic strapPipe insulator

Vertical pipe support

Strut cushion clamp

Common pipe fittings

Many of the pipe fittings used in hydronic systems are the same as used in conventional water supply systems.

Couplings: (standard and reducing)

Standard Reducer coupling

Elbows: 90 degree and 45 degree

90 degree45 degree

Street elbows: (90 and 45 degrees)

Street 90 Street 45

Tees: (Standard and reducing)

Standard Reducing Tee

Threaded adapters: (Male and female)

Male adapter Female adapter

Unions

Ball valves

Sweat ball valve NPT ball valve

Gate valve

Boiler drain valve

Boiler Drain T

Baseboard elbow