How long should I water?

A 0.25 gallon per minute (0.95 l/m) bubbler will put out 7.5 gallons (28,4 liters) in 30 minutes. The volume of the 4” x 36” RWS tube (10,2 cm x 91,4 cm) is about 2 gallons (π r² h = 452 cubic inches or 1.98 gallons) (7,6 liters), less when the irrigation hardware is factored and much less if pea gravel is used. The soil type also plays a big role. The key is not to put more water into the tube than the tube and soil can absorb during that watering period. As a general rule, shorter watering volumes will limit overflows.