How to select the right size of pressure tank for your usage?

07 August 2020

It is very important to have the right size of water pressure tank for your usage. Whether you are installing a new one or upgrading your current pressure tank, selecting the right size of pressure tank for your pump system will ensure that your pump performance is optimized and sustained for as long as possible. That is the reason why pressure tanks have a wide range of sizes and depend on your unique situation and demands for your usages, suppliers can offer you hundred kinds of pressure tanks.

So in this article, we would like to guide you the correct way to select the right size of pressure tank.

 What is a water pressure tank?

 

 

 

 

 

 

 

 

 

Pressure tanks have a wide range of sizes

A pressure tank (pressure vessel, booster tank) is a metal container that can vary in size from 5L up to 3000L. There is a rubber membrane inside the tank that separates a chamber of air from the water.

The pressure tank creates the water pressure by using compressed air to drag down on the water. When opening a valve, the compressed air in the tank will push out the water. The water is pushed all through the plumbing in the apartment until the pressure drops to a preset low on your pressure switch.

 

Design & description of Varem pressure tanks

A pressure tank preserves the water pressure in the household/factory and more importantly, protects the life of the pump. Every time a faucet turns on, a toilet flushes, or someone takes a shower, water is supplied from your pump. The pressure tank holds a certain amount of water to take out to meet these needs before requiring the pump to start on. This extends the time between the pump turning on and turning off. Let's think about that! If you don’t have a pressure tank, every time you open a faucet the pump will kick on, and when you close the faucet, the pump shuts off. It can cause your pump to damage early and require an expensive replacement that could have been avoided.

Why do we need to select the right size of pressure tank

 

 

A booster system with pressure tank

If you select the wrong size, the effect of the pressure tank will be gone. As we analysed before, it can cause the short cycle of your pump. Short-cycling is a term for when a pump turns on and off too frequently. The more a pump must run, the more wear and tear occurs to the pumping mechanism and the electric motor. Sizing a water pressure tank properly will greatly reduce the risk of early pump failure. Besides that, it increases energy use and can cause a water pump to run excessively which makes premature failure of your pump. In addition, water pressure is affected when using various faucets at the same time.  If you're installing a new water pressure tank or replacing an old one, you can determine the right size of pressure tank for ideal water pressure and pump performance by the formula below.

The formula to find the right size of pressure tank

 

A horizontal pressure tank from Varem brand

Firstly, find these parameters:

p2: Minimum working pressure (relative, bar);

p1: Maximum working pressure (relative, bar):

Q: Maximum flow rate required (l /min);

P: Pump power (kW);

Do you know that the most pressure tanks are rated by their drawdown capacity. The drawdown capacity is the amount of available water that is stored in the pressure tank between the pump switching on and off.

The formula finds the capacity Vt of a pressure tank large enough to give an adequate water storage (R) for the booster system. The useful storage depends on maximum flow rate required and pump power P, on the basis that, with the system running, the air between the membrane and the metal shield of the autoclave is affected by an isothermal compression. Found the water pump's litre per minute (l/min) capacity which is stated in the manufacturers specifications.

So:

- The product (p+1)*V remains constant.

- pn+1 is the absolute pressure (pna=pnr+paatm), that also considers even the atmospheric pressure.

- Observational methods allow calculation of the storage R according to the formula R=Q*K, where K is a coefficient of the pump power.

P (kW) 1 2 3 4 5 6 8 10
K (min) 0,25 0,33 0,42 0,50 0,58 0,66 0,83 1,00

Given this parameters, the formula is as follows:

The capacity of the chosen tank will be the closest to Vt , rounding up. Alternatively the approximations in the table below can be used.

Table of nominal capacity by working pressure

Absolute precharge pressure + P atm (bar) 1,8 1,8 1,8 2,3 2,3 2,8 2,8 2,8 3,3 3,3 3,3 3,8
P2 + P atm (bar) 2 2 2 2,5 2,5 3 3 3 3,5 3,5 3,5 4
P1 + P atm (bar) 3 3,5 4 3,5 4 4 4,5 5 4,5 5 5,5 5
Tank nominal capacity Tank draw down R (lt,)
5 1,5 1,9 2,3 1,3 1,7 1,2 1,6 1,9 1,0 1,4 1,7 1,0
8 2,4 3,1 3,6 2,1 2,8 1,9 2,5 3,0 1,7 2,3 2,7 1,5
1,5 5,7 7,3 8,6 5,0 6,6 4,4 5,9 7,1 4,0 5,4 6,5 3,6
20 6,0 7,7 9,0 5,3 6,9 4,7 6,2 7,5 4,2 5,7 6,9 3,8
24 7,2 9,3 10,8 6,3 8,3 5,6 7,5 9,0 5,0 6,8 8,2 4,6
25 7,5 9,6 11,3 6,6 8,6 5,8 7,8 9,3 5,2 7,1 8,6 4,8
35 10,5 13,5 15,8 9,2 12,1 8,2 10,9 13,1 7,3 9,9 12,0 6,7
40 12,0 15,4 18,0 10,5 13,8 9,3 12,4 14,9 8,4 11,3 13,7 7,6
50 15,0 19,3 22,5 13,1 17,3 11,7 15,6 18,7 10,5 14,1 17,1 9,5
60 18,0 23,1 27,0 15,8 20,7 14,0 18,7 22,4 12,6 17,0 20,6 11,4
80 24,0 30,9 36,0 21,0 27,6 18,7 24,9 29,9 16,8 22,6 27,4 15,2
100 30,0 38,6 45,0 26,3 34,5 23,3 31,1 37,3 21,0 28,3 34,3 19,0
200 60,0 77,1 90,0 52,6 69,0 46,7 62,2 74,7 41,9 56,6 68,6 38,0
300 90,0 116 135 78,9 103 70,0 93,3 112 62,9 84,9 103 57,0
500 150 193 225 131 172 117 157 187 105 141 171 95,0
750 225 289 337 197 258 175 233 280 157 212 257 142
1000 300 386 450 263 345 233 311 373 209 283 343 190
1500 450 579 675 394 517 350 467 560 314 424 514 285
2000 600 771 900 526 526 467 622 747 419 566 686 380

Above is the standard formula by the manufacturer for calculating the right size of pressure tank for your usage. However, in order to calculate the right size of pressure tank in reality, more careful investigation and analysis is needed due to many impact factors. If you need to buy a pressure tank for your company or your house , please do not hesitate to call our hotline (84) 283 915 2282 - (84) 0915 78 22 82 for advice and answers quickly.

 

Varem is a world leader in the production of pressure tanks

Delton Marine is proud to be the distributor of genuine Varem pressure tank products (Italia) in Vietnam with experienced staff. For more details on Delton Solutions 's existing products, please visit here: Varem Pressure Tank