How this calculator works
The International Plumbing Code gives a maximum distance between supports for each pipe material. We divide the run by that distance, round up to whole spans, and add one for the support at the end. Pipe that goes straight up is supported at much longer intervals, about 10 ft for most materials and 15 ft for cast iron.
Worked example: a 40 ft horizontal run of PVC (4 ft maximum) needs 11 hangers (every 4.00 ft); the same run in 3/4 in copper (6 ft) needs 8, and in PEX (32 in, or 2.67 ft) 16. Add 1 support for an 8 ft vertical run.
Assumptions and sources
- These are the maximum spacings in the International Plumbing Code table of hangers and supports (IPC Table 308.5). Cast iron may be supported every 10 ft if 10 ft lengths are used with a support at every joint. Many areas use the Uniform Plumbing Code or their own amendments with different numbers, and pipe makers can ask for closer spacing (PEX and CPVC in hot water, for instance), so check your local code and the pipe maker. Add a support close to every change of direction and fitting, and where a valve or heavy load is carried. The vertical count is the least: an extra support at each floor and at the base of a long stack is normal.
The formula and a worked example are shown above, so you can check any result by hand. Read how we calculate and check our numbers. Results are estimates for planning: supplier products vary, so check the size printed on the label.
Maximum hanger spacing by pipe (IPC)
The greatest distance between supports the model code allows, with the hangers a 40 ft horizontal run needs.
| Pipe | Horizontal | Vertical | Hangers for 40 ft |
|---|---|---|---|
| PVC or ABS | 48 in (4.00 ft) | 10 ft | 11 |
| Copper, 1-1/4 in and smaller | 72 in (6.00 ft) | 10 ft | 8 |
| Copper, 1-1/2 in and larger | 120 in (10.00 ft) | 10 ft | 5 |
| PEX | 32 in (2.67 ft) | 10 ft | 16 |
| CPVC, 1 in and smaller | 36 in (3.00 ft) | 10 ft | 15 |
| CPVC, 1-1/4 in and larger | 48 in (4.00 ft) | 10 ft | 11 |
| Cast iron | 60 in (5.00 ft) | 15 ft | 9 |
Tips before you buy
- Plastic pipe sags far sooner than metal, which is why PVC and CPVC need supports more often than copper. Hot water makes it worse.
- Use hangers made for the pipe: a metal strap that bites into plastic can wear it, and copper wants a copper-compatible hanger to avoid corrosion.
- A drain also needs its fall: support it at the slope the code asks for, not level.
- Put a support close to each change of direction and at each valve so the weight does not sit on a joint.
- Leave PEX and plastic room to expand: do not clamp it tight, and let it slide in the hanger.
Tools & materials for this project
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Frequently asked questions
How far apart should pipe hangers be?
It depends on the material: PVC and ABS 4 ft, copper up to 1-1/4 in 6 ft, copper 1-1/2 in and larger 10 ft, PEX 32 in, CPVC 3 ft (1 in and smaller) or 4 ft, and cast iron 5 ft, from the IPC table. Check your local code.
How many pipe hangers do I need for 10 feet of PVC?
4: a 10 ft run is three spans of 4 ft or less, so four supports including both ends.
How often does vertical pipe need supports?
About every 10 ft for PVC, ABS, copper, PEX and CPVC, and every 15 ft for cast iron, and at least one for each run.
How far apart do PEX supports go?
32 in (2.67 ft) for horizontal runs, and about 10 ft for vertical runs with the usual guides.
Does the spacing change for hot water?
The code table does not change, but pipe makers often ask for closer support for plastic pipe in hot water. Follow the stricter of the two.
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Estimates only. Results assume standard materials and simple shapes. Supplier products vary, and the final call on quantity, structure and safety is yours. Check your local code and your supplier's guidance before ordering.