Patio umbrella bases
Patio umbrella bases must be heavy enough to keep the umbrella stable and secure. The bases can be produced as metal stands, plastic containers filled with water or concrete filled bases. Patio umbrella bases usually weight more than 40 pounds. When you chose the base and its weight you should consider if the umbrella is to be attached to a patio table. If attached to a table it will require less weight. For extra safety you may buy a bit heavier base than you actually need. Umbrella bases and safety:
For safety reasons patio umbrellas should be securely fastened to their bases or to other stable and heavy construction. This will prevent cases of big patio umbrellas being caught by the wind and landed in a crowded area which can lead to lethal incidents.Weight of the umbrella base:
There is a relation between the size of the patio umbrella and the weight of the base which should be used.
The weight of the base is also determined by the way the umbrella is utilized – is it placed through a table or is it freestanding one. It is very critical to choose the right umbrella base in accordance with these weight-size relations. 35-40 pound bases can be used with small umbrellas (up to 7.5 foot ones) which are attached to a garden table. Bigger basses should be used for free standing umbrellas though. 
9-foot patio umbrella put through a table is to be fixed to 50-55 pound base while 70-75-pound base should be used for free standing one with the same size. The most secure outdoor umbrella bases are these of 100 pounds and more. They can be used with any umbrella up to 11 feet without any worries. Heavy-duty bases should be used to support patio umbrella in windy areas.URL.biz - Gardens