Section 37 · Reference · Print
Field cheat sheet
Every formula and rule of thumb from this knowledge base, compressed onto a single sheet. Print it, laminate it, bolt it to the pump house wall.
HYDRAULIC RAM PUMP — FIELD CHEAT SHEET
sizing formulas & rules of thumb · RamPump Knowledge Base · print at 100%, A4 or Letter
q = η · Q · H / h
delivered flow · η ≈ 0.6 · the whole pump in one line
1 · Know your site
| H | fall — source surface → ram (the power) |
| h | lift — ram → delivery tank surface |
| L | drive pipe length, intake → ram |
| Q | drive flow through the ram |
| q | delivered flow (what you get) |
2 · Core formulas
Delivered flowq = η·Q·H/h
Input powerP₁ = ρg·Q·H
Output powerP₂ = ρg·q·h
Hammer spikeΔp = ρ·c·Δv
Wave returnt_w = 2L/c
Spin-up timet ≈ L·v/(g·H)
Pipe diameterD = √(4Q/(πv))
Friction (Darcy–Weisbach)h_f = f·(L/D)·v²/2g
ρ = 1000 kg/m³ · g = 9.81 m/s² · use Q in m³/s for power · Re = vD/ν, ν ≈ 1.0×10⁻⁶ m²/s · turbulent: f ≈ 0.020–0.025 for new pipe
3 · Wave speed by pipe
| steel | copper | PVC | HDPE | hose |
|---|---|---|---|---|
| 1200–1400 | 1000–1300 | 300–500 | 250–400 | ✗ |
m/s · softer pipe = weaker hammer
4 · Rules of thumb
- Fall H ≥ 1 m comfortable · 0.5 m absolute floor
- Drive pipe L = 3–7 × H · rigid · constant Ø · straight — no hose, ever
- Velocity 1–2 m/s at valve closure
- Lift ratio h/H 2–6 sweet spot · ≤ ~10 workable
- Friction budget drive h_f ≤ 10% of H · delivery ≤ ~15% of h
- Delivery pipe ≈ ½ drive Ø · rated above full static head
- Air chamber 20–50 × per-beat volume
- Snifter hole ≈ 1 mm near the check valve
- Intake submerged 2–3 Ø · 1–2 mm screen · off the bottom
- Beat rate 30–100 /min, steady
- Waste water channel clear of the pad — it never stops
5 · Drive pipe Ø at 1.5 m/s
| Q (L/s) | 0.5 | 1 | 2 | 4 | 8 | 15 |
|---|---|---|---|---|---|---|
| Ø (mm) | 25 | 32 | 50 | 63 | 90 | 125 |
| (inch) | 1 | 1¼ | 2 | 2½ | 3½ | 5 |
Round up to the nearest nominal size · steel preferred
6 · Output per 1 L/s drive flow
η = 0.6 — multiply by your Q · runs 24/7
| h/H | L/day | m³/day |
|---|---|---|
| 2 : 1 | 25 900 | 25.9 |
| 3 : 1 | 17 300 | 17.3 |
| 4 : 1 | 13 000 | 13.0 |
| 5 : 1 | 10 400 | 10.4 |
| 6 : 1 | 8 600 | 8.6 |
| 8 : 1 | 6 500 | 6.5 |
| 10 : 1 | 5 200 | 5.2 |
7 · Tune the beat
- Fast, fluttery → weight outward (heavier)
- Slow, stalls → weight inward (lighter)
- Banging delivery → recharge chamber air
- Air spits → seal drive joints · deepen intake
- Beats, no delivery → clean check valve · ratio too high?
8 · First start
- Purge drive pipe until flow runs solid
- Push waste valve down & release ×3–4
- Open delivery valve slowly
- Tune weight → recheck in one week
NEVER — hose drive pipe · thin-wall PVC chamber · stand over a beating chamber · let it freeze full