FAQ
TL;DR: A solar pool heater works when head loss ≤ pump pressure; every 10 m of 20 mm hose adds 0.4 m head [Engineering Toolbox]. “Connect several shorter sections in parallel” [Elektroda, zimny8, post #16594946]
Why it matters: Matching hose length to pump head cuts power draw and keeps water moving, boosting daily heat gain.
Quick Facts
• Friction loss: 100 m of 20 mm hose ≈ 4 m head at 1 m³/h [Engineering Toolbox].
• Recommended flow: 2–4 L/min · m² collector surface [US DOE Solar Guide].
• Typical CO circulation pump: 4 m head, 3000 L/h, 60 W draw [Grundfos Data, 2023].
• Diaphragm well pump: 70 m max lift, ~200 W input [Elektroda, teskot, post #16594872]
• 12 V submersible pump: 800 L/h, 22 W draw [Elektroda, Norek+, #19540328].
1. How do I calculate the maximum hose length my pump can handle?
Check the pump curve for available head (pressure). Multiply hose length by 0.04 m head per metre for 20 mm ID at 1 m³/h [Engineering Toolbox]. Stop adding hose when total head (hose + height) is 10-15 % below pump head. Example: a 4 m-head pump supports ≈85 m of 20 mm hose on level ground.
2. Which matters more—hose length or diameter?
Diameter dominates. Halving diameter increases friction about sixteen-fold at the same flow. Extending length only raises friction linearly [Engineering Toolbox]. Up-sizing from 20 mm to 25 mm can double allowable length for the same pump.
3. Can I leave a dirty-water pump submerged while swimming?
Yes, but users reported strong vibration and electrocution risk [Elektroda, zimny8, post #16595865] Remove the pump during bathing or use a low-voltage (12 V) unit with RCD protection.
4. Is a high-pressure diaphragm pump a better choice?
It delivers up to 70 m head yet draws about 200 W, so it can push long, narrow hoses [Elektroda, teskot, post #16594872] Noise is high, and cheap clones may fail early [Elektroda, teskot, post #16594880]
5. Does splitting the hose into parallel sections help?
Yes. Two 50 m lines in parallel cut friction roughly four-fold, letting a low-pressure pump flow freely [Elektroda, gruniu, post #16598673]
6. How should I mount a temperature sensor on a plastic hose?
Avoid drilling. Strap the probe flat against the hose, wrap with aluminum tape, then insulate with foam. This gives ±1 °C accuracy without leaks [“REX-C100 Manual”].
7. Do I need a controller or can the pump run nonstop?
Continuous flow evens pool temperature but wastes 20–60 W overnight. A simple thermostat that starts the pump when collector is ≥3 °C hotter than pool cuts 30–50 % energy use [US DOE Solar Guide].
8. What’s the energy balance?
A 10 m² collector delivering 3 kWh/day can raise a 20 m³ pool by 0.13 °C. Running a 60 W pump eight hours adds only 0.48 kWh—16 % of the solar gain [DOE, 2022].
9. What pump spec suits 100 m of 20 mm hose?
Look for 5 m head at 1 m³/h and ≤100 W input. Many circulation pumps (e.g., Grundfos 25-40) meet this [Grundfos Data, 2023].
10. How do I cut pump noise and vibration?
Suspend the pump on silicone cords or place it on a rubber mat. Submerging it 1 m lowers audible noise by ≈25 dB [Baxter, 2019].
11. Edge case: what if flow nearly stops?
Stagnant dark hose can hit 80 °C under full sun; water may flash to steam, blocking flow and deforming plastic [Solar Pool Design FAQ]. Limit outlet temperature to 60 °C with a controller.
12. How-To: Start up and deaerate the system
- Fill hose fully from tap until water exits collector.
- Close tap, connect pump, and power it for 30 s.
- Slightly loosen the highest joint; let trapped air hiss out, then retighten.
Done—no sputtering [Elektroda, gruniu, post #16594828]
. On a garage roof or other ground floor buildings it will be OK. The pump goes from 9am to 5pm when the sun is warming. It is really worthwhile to do such a simple installation.
