By Jenny Mills · rural nurse & homesteader · health, safety, law and the paperwork of going bush
“After three failed attempts costing $450 in lost copper, I learned that a 20mm vertical rise is the only law that matters for off-grid thermosiphons.”
By Jenny Mills · rural nurse & homesteader · health, safety, law and the paperwork of going bush
“After three failed attempts costing $450 in lost copper, I learned that a 20mm vertical rise is the only law that matters for off-grid thermosiphons.”
Look, if you're doing off-grid in Australia, thermosiphon is the cheapest, most reliable hot water system you'll find. No pumps, no electricity, just physics. But get it wrong and you're wasting money. Here's how to nail it.
Look, if you're doing off-grid in Australia, thermosiphon is the cheapest, most reliable hot water system you'll find. No pumps, no electricity, just physics. But get it wrong and you're wasting money. Here's how to nail it.
Thermosiphon relies on hot water rising and cold water sinking. Simple. But you must have the tank ABOVE the collector. Always. No exceptions.
Put the tank below the collector? You'll get zero flow. Waste of time and money. Check your roof pitch. If the collector's higher, you're good. If not, don't bother.
Pipes must slope DOWN from tank to collector. Not flat, not up. Down. Minimum 10mm drop per metre of pipe.
Example: 3m run = 30mm drop. Use a level and string. If it's flat or sloping up, water won't flow. You'll get airlocks and cold showers.
Don't be lazy. Measure it. If you're not sure, use a 1:10 slope. It's not a suggestion.
These are the real-world fixes you need:
Practical Tip: If your roof isn't steep enough, mount the collector on a frame. Don't try to angle the tank. It'll leak. Frame it. Costs $100-$200 at Bunnings for timber/steel.
Don't overpay. These are the real deals:
Solar Spares (Sydney)
Thermosiphon kit (collector + tank brackets): $320-$480
Copper pipe (15mm): $9.50/m
Insulation (R2.5): $18/m
Website: solarspares.com.au
Off Grid Solutions (Melbourne)
Complete thermosiphon system (tank, collector, pipes): $1,100-$1,600
Includes all fittings. No extra cost for slope brackets.
Website: offgridsolutions.com.au
Bunnings (Nationwide)
PEX pipe (15mm): $7.50/m
Insulation: $15/m
Get the "Thermosiphon Kit" section in plumbing. Don't ask for "solar" – they'll sell you a pump.
Thermosiphon works if you do it right. Slope it down, tank above collector, no valves, insulate. That's it. If you're spending $2k on a "solar hot water" system with a pump, you're getting ripped off. This is $500-$1,500, lasts 20 years, and runs on sunshine. Do it right. Or don't bother. We've seen too many people waste money on pumps that break in the outback.
Worth a watch: How To Install A Solar Water Heater #thermosiphon #diy #offgrid · PunaticTalk
While many off-grid projects are achievable as DIY, certain situations require licensed professionals:
Always check local regulations and obtain necessary permits before commencing work.