Flogas 7kg Butane Refill 21mm

The 7kg Flogas Butane is the mid-size butane cylinder — larger than a camping canister, smaller than the 13kg. It suits caravans, narrowboats, weekend campers, and households who want a manageable cylinder for occasional indoor heater or cooker use. For regular home heating, the 13kg gives better value per kilogram and fewer reorders.

If you are using a patio heater most evenings, butane is not the right gas for outdoor use — it struggles to vaporise properly below around 5°C and output drops noticeably on cold evenings. For regular outdoor patio heating, a propane cylinder such as the 11kg Leisure Patio Gas or 10kg Gaslight is a more reliable choice.

Run-time depends on your heater's output. Butane has a calorific value of approximately 13.7 kWh per kg, so a 7kg cylinder contains around 96 kWh of usable energy. At a typical 3kW output, that is approximately 30–32 hours of continuous use; at 4kW, around 24 hours. At moderate use — two hours per evening — a 7kg cylinder typically lasts two to three weeks.

One important caveat: if the cylinder is stored anywhere unheated — an outdoor shed, porch, or utility room — butane's vaporisation limit (around 2°C) means heat output will fall before the cylinder is actually empty. In cold weather you may experience what feels like a cylinder running out when usable gas still remains but is not vaporising. Storing the cylinder indoors at room temperature before use will restore normal output.

Yes — the 7kg Flogas Butane is a practical choice for caravanning and motorhome use in mild conditions. It connects via the standard 21mm clip-on fitting and works with most UK caravan cookers, blown-air heaters, and portable appliances designed for butane. The 7kg size is easier to handle and store in a caravan gas locker than the 13kg.

The key limitation is temperature. Butane stops vaporising reliably below around 2°C, which means pressure drops and appliances weaken or cut out on cold nights. For spring and summer touring in the UK this is rarely an issue, but for autumn or winter caravanning propane is a more reliable choice. Propane performs consistently down to around −42°C and will not lose pressure overnight. If your caravan gas locker and appliances are compatible with propane, the 5kg Gaslight is a convenient lightweight alternative for touring use.

Before switching, check the regulator currently fitted in your caravan — a blue 21mm clip-on means butane; a red 27mm clip-on means propane. They are not interchangeable.

Yes — butane is suitable for use with portable gas heaters designed for indoor use, and the 7kg cylinder is compatible with any such heater that takes a 21mm clip-on connection. The critical requirement is ventilation. Always run a portable gas heater in a room with a window slightly open or another source of fresh air circulation. The danger in a poorly ventilated space is not simply that oxygen is depleted — it is that incomplete combustion produces carbon monoxide (CO), an odourless, colourless gas that causes fatalities in the UK every year from poorly ventilated gas appliances. Complete combustion produces CO2 and water vapour; restrict the air supply and the same appliance produces CO. Never use a portable gas heater in a bedroom while sleeping, in a tent, or in any space with no airflow.

Fit a carbon monoxide alarm in any room where a portable gas heater is used — this is current UK safety guidance and the single most effective precaution against CO exposure.

Check the heater's manual before use — it will confirm whether it is rated for indoor use and specify the minimum ventilation required. Appliances labelled for outdoor use only should never be operated indoors regardless of gas type.