Vancouver has had many dry spells the last few years, stressing young street trees. Not far from my house but beyond reach of my 3 hoses is a Stewartia whose leaves look like potato chips; it's still alive, and its older brothers got past that stage. If I dumped a bucket of water on it, most of it would run off into the street. The Vancouver Parks website vancouver.ca/parks/trees/treebro1.htm recommends slow watering twice a week, but their watering truck cannot come that often. I use a 5 gallon pail, and around 33" of 1/8" tubing (23 liters, 80cm, 3mm inner diameter) which I got from a hardware store. The siphon tubing needs a weight at both ends - for example a large nail, attached with wire. With that small size of tubing, the pail takes 3 hours to empty, so the water goes deep, instead of spreading near the surface where it would run off, evaporate faster and encourage shallow roots. I can't carry that weight, but my car can. 2 half-full buckets are easier to manage, and less likely to splash.