A bored log pipe is a straight log 10-15 cm across drilled end to end with a long auger, one end tapered to push into the socket of the next log and sealed with tallow, pitch or clay. It lasts 15-30 years in wet service, but only if it stays permanently wet and under low pressure, so design for under 3 m of head and make sure the wall left at each socket is thick enough not to split.
A bored log pipe is a hollowed tree trunk used as a water pipe. Cities used them for centuries because they need only a long auger and rot-resistant wood, and they survive as long as they stay wet.
What The Parent Page Specifies
Select straight logs 10-15 cm in diameter, bore a hole through the centre with a long auger (a large drill bit with a T-handle), joint logs by tapering one end and socketing it into the next, and seal joints with tallow, pitch or clay. Elm is the preferred wood because it resists rot when wet. Bored log pipes last 15-30 years in wet service.
Pressure: Two Pages Disagree, Use The Lower
Pipe Making gives bored log up to 15 psi, which is 15 ÷ 1.42 = 10.6 m of head. Wooden Pipes designs bored wooden pipe for under 3 m of head. Design for the lower figure and put a break pressure tank in any line with more fall. A joint that seeps at 3 m can burst at 10 m.
Wall Thickness Decides Whether It Splits
Wall = (log diameter − bore) ÷ 2. At the socket the wall is thinner, because the end is reamed wider:
| Log | Bore | Socket | Wall along the log | Wall at the socket |
|---|---|---|---|---|
| 10 cm | 5 cm | 7 cm | 2.5 cm | 1.5 cm |
| 15 cm | 5 cm | 9 cm | 5.0 cm | 3.0 cm |
| 15 cm | 7.5 cm | 10 cm | 3.75 cm | 2.5 cm |
| 15 cm | 10 cm | 12 cm | 2.5 cm | 1.5 cm |
The socket sizes are my assumed example (the pipe must slip over a tapered spigot of about the bore diameter plus a margin). A 1.5 cm wall around a joint under pressure splits along the grain. So choose a log diameter that leaves at least about 3 cm at the socket, and band the socket with iron or cord if the wood is thin. The 3 cm figure comes from the rows above, a judgement, not a sourced limit.
What You Need
- Straight, sound, rot-resistant logs: elm per the parent page; the wooden-pipes page also names black locust, white oak, bald cypress and alder
- A long auger and a means of holding the log: see Drill and Auger
- A reamer for the socket and a drawknife or adze for the taper
- Sealant: tallow, pine pitch or clay. Do not use creosote or coal-tar products on drinking water pipe
- Iron bands or cord for the socket ends
- Trench deep enough to keep the pipe wet and unfrozen
Method: Bore, Taper, Ream, Join
Step 1: Fix the log horizontally on supports, level and straight along its axis.
Step 2: Bore from both ends so the holes meet in the middle, as the wooden-pipes page describes, and as the pipe-making page advises for logs over 2 m. Sight along the bore; a misaligned meeting leaves a step that catches debris.
Step 3: Taper one end into a spigot with a drawknife.
Step 4: Ream the other end into a socket, keeping the wall thickness above.
Step 5: Drive the spigot into the next socket, sealed with tallow, pitch or clay, and band the socket.
Step 6: Lay in a trench to a steady fall, and fill the pipe with water as soon as it is laid.
Keep It Wet And Below Frost
A wooden pipe that dries and re-wets develops cracks and leaks. Bury it below the frost line and keep it full; if the line must be drained for repair, refill as quickly as you can (Pipe Making). Friction in a wooden pipe is modest: roughness coefficients of 80-100 apply (Pipe Sizing), so at household flows the pressure and the rot, not friction, set the limits.
Common Mistakes
- A thin wall at the socket.
- Drying the pipe out.
- Using more than 3 m of head without a break tank.
- Sealing with creosote or coal tar.
- Using softwood. It rots faster.
Safety
Boring tools, heavy logs and hot pitch cause injuries
A log can roll and crush; wedge it. A long auger can kick or jam; keep hands clear and use both hands on the T-handle. Heated pitch burns and flames; keep it away from the fire’s edge. Wood dust irritates the lungs: wear a cloth over the face. Never use treated or creosoted timber for drinking water.
What’s Next
- Learn next: Clay Pipe — a longer-lasting hand-made pipe for low head
- Combine with: Wooden Pipes — the wider history and wood choices