One pipe size up fixes most pressure problems

Friction pressure drop scales with 1/d⁵ — a modest increase in diameter slashes losses.

Why it works

From Darcy–Weisbach at fixed flow. Going from 25 mm to 32 mm pipe cuts friction loss by ~70%. Bigger pipe is usually cheaper than a bigger pump.

Do it exactly

Estimate with the rule, then check it against the calculator that models it properly.

Open Pipe Flow & Pressure Drop →

More in Mechanical

• The bolt-torque shortcutTightening torque ≈ 0.2 × preload × bolt diameter (dry steel).
• Torque mostly fights frictionRoughly 90% of tightening torque is lost to friction; only ~10% actually stretches the bolt.
• Deflection limits: span/250Keep beam deflection under span/250 generally, span/360 where people will notice a bouncy floor.
• Depth beats width, cubedDouble a beam’s depth and its deflection drops 8-fold. Double its width and it only halves.

Browse all 96 rules of thumb →