I always drink more than 3litres per day, & i when i mesure my blood pressure it's always around 10, can drinking a lot of water lower blood pressure? ?

100?: If you're alive you can't have a BP of 10 (at least not in the units we use: millimeters of mercury). I assume you mean "100". This is a little low for a large man, but perfectly normal for a 21 year old female. Drinking water does not lower your BP and, assuming it's hot in algeria, drinking 3 liters a day is normal, healthy, and necessary to replace the water you lose thru perspiration.