Connect 4/7 mm micro drip tubing to 1/4 inch drip tubing
How to join 4/7 mm (4 mm ID x 7 mm OD) and 1/4" (0.170" ID x 0.250" OD), and what stops it leaking.
Not a direct fit. Joining 4/7 mm micro drip tubing to 1/4 inch drip tubing needs a 4/7 mm to 1/4 inch drip tubing adapter.
The part to buy
4/7 mm European micro tube (4 mm bore) and US 1/4 inch tube (0.170 inch, about 4.3 mm bore) are close but not the same, so barbs do not swap cleanly between them. A 4/7-to-1/4 inch coupler joins a European kit to US fittings when you are mixing parts.
The fractions of a millimetre matter here. A 1/4 inch barb pushed into 4/7 mm tube splits it; a 4/7 mm barb in 1/4 inch tube weeps. Use the matched coupler.
Related connections
Sources: 4mm (4/7mm) micro hose data, Hozelock · 1/4in polyethylene drip tubing 0.170in ID x 0.250in OD spec, Drip Depot · 1/4in barbed drip fittings for 0.140-0.170in ID tubing, DIG Corp