Drinking 7lt a day

Rain will struggle to get to the soil in the pot, due to the plants' leaves covering most of the exposed surface. Poor absorption often happens when the soil gets over dry, then becomes "hydro phobic", meaning rather than being absorbed, the water just runs straight through the pot without doing much watering of the plant. The best way to solve this is to place a hose in the pot and set the water flow so that it is just dribbling out, not much more than drips, and leave it in the pot for a few hours or even overnight. This slow dribble will be absorbed bit by bit and eventually all the soil will become rehydrated, a bit like blowing up a balloon, - lots of little breaths and not a single huge blast. Another way is to give the 7-10 litres in half litre doses over a number of hours, say half a litre every 30-45 minutes. It is the same "balloon blowing up" principle, a bit of absorption every so often, rather than all 7-10 litres all in one go. Each half litre will soak in a bit and each subsequent half litre will soak just a bit more than the last, swelling up the soil progressively and thereby preventing the water from running straight through the pot without being absorbed. Watering to 20% run off, that is, until water comes out of the bottom of the pot, will keep the soil more evenly moist and prevent it from becoming "hydro phobic" once again. Hope this helps, Organoman.