Pipe, hose and fittings are the plumbing of a grow room – the parts that move nutrient from the tank to the plant and back. Get the sizing right at the start and a system runs for years; get it wrong and you spend every week chasing leaks.
Pipe sizes and what they are for
Size
Typical use
4mm micro tube
Individual drippers to each plant
13mm LDPE
Standard feed line on small to mid systems
16mm LDPE
Main runs on larger drip systems
25mm
Flood and drain, fill and drain lines, high flow
32mm and up
Return lines and large recirculating systems
Sizes are usually quoted as outside diameter for LDPE pipe and inside diameter for flexible hose, which is the single most common source of ordering the wrong part. Check which figure a listing is quoting before you buy.
Barbed or compression?
Barbed fittings push into the pipe and hold on friction, usually with a clip. Cheap, fast, and fine for low pressure. Warm the pipe end in hot water and it goes on far more easily.
Compression fittings clamp the pipe with a threaded collar. More expensive, far more secure, and the right choice on anything pressurised or anywhere a leak would reach a floor you care about.
What you actually need
A working system is pipe plus: elbows and tees to change direction and split, straight connectors to join runs, end caps, and taps or valves at every branch so you can isolate one line without shutting the whole system down. That last one is what separates a system you can maintain from one you have to drain.
Getting it watertight
Cut square. An angled cut will not seal on a barb. Use a proper pipe cutter, not scissors.
Support the weight. A full 25mm line is heavy; unsupported runs sag and pull fittings apart over time.
PTFE tape on threads only – never on a barb or a compression joint, where it prevents the seal rather than making one.
Test with water before plants go in. Run it for an hour and check every joint. Always.
We are a hydroponics shop in Croydon and we build these systems over the counter, so we can put a parts list together rather than leaving you to guess at fitting sizes. Bring us a drawing or the dimensions of your room. Discreet UK and European delivery, and excellent customer reviews on Trustpilot.
