08 08 2021
The difference between bladder and diaphragm pressure tanks|Aquasky

The difference between bladder and diaphragm pressure tanks|Aquasky


The common tanks in the PUMP water supply system can be divided into bladder type and diaphragm type according to the structure.



Please see the structure of the diaphragm tank below.

The water storage pressure tank can be divided into two areas: the upper is the water storage area and the lower is the air pressure area. The two areas are separated by a rubber diaphragm.

The tank is pre-filled with 30 psi pressure from the sealing nozzle before leaving the factory. When the tank begins to store water, the weight of the water will squeeze the rubber toward the air pressure zone. At this time, the pressure in the air pressure zone will become larger and larger (the air can be compressed). When the pressure is greater than the preset high-pressure value, the pump stops pumping water. On the contrary, when there is water demand (ex: boiling faucet...etc.), the air squeezed in the air pressure zone is released, and the rubber diaphragm is squeezed. The water squeezed toward the joint, causing the water to flow out.


Bladder type:

The operating principle is the same as that of a diaphragm tank. The pressure difference caused by the squeezing of the air can reach the storage and discharge of water.

The biggest difference between the diaphragm tank and the bladder tank is the rubber diaphragm and the water outlet in the tank. The rubber diaphragm of the bladder tank can be replaced and locked on the docking flange with a crew pair.


Both have their own advantages in use. The diaphragm tank provides a stainless steel joint and is directly welded to the tank itself to reduce the possibility of air leakage. Therefore, it is not necessary to check the air leakage of the tank frequently. What’s more, it can be seen from the structure of the tank. There is an extra layer of FDA-grade PP plastic in the tank, which prevents water from directly touching the metal itself, so it is also suitable for drinking water systems.


The advantage of the bladder type is that the bladder can be replaced, so it is suitable for large tanks’ design ex: 2000L, 3000L or 5000L …etc. In terms of cost, only the bladder needs to be replaced instead of the entire tank. Another risk of damage to the bladder tank is air leakage. Due to the joint is locked by the screw and the connecting flange, the rubber cap is pulled due to different water pressures, which may easily lead to air leakage and elastic fatigue of the rubber cap. Need preventive replacement of rubber caps.




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