09-16-2016, 05:31 AM
There are additional benefits to a pressure tank. It provides surge capacity, which will allow greater flow than the pump alone may be able to provide. If someone is running the kitchen sink, while someone else is in the shower, and someone then flushes a toilet, the pump may not be able to keep up with the demand. This is especially problematic in a system which relies upon an on demand hot water system. The flow rate may drop below the threshold of the unit, causing it to shut down. Not so nice for the person in the shower. Add a washing machine and a dishwasher and the problem gets worse.
The pressure tank also provides stable flow which may otherwise lag during pump startup. When you open a faucet, the time between the initiation of flow and a drop in pressure sufficient to trigger the pump would be noticeable in the output pressure and flow rate. If the flow rate is sufficiently restricted, say by only opening the faucet part way or by a restrictive shower head, a surging effect can occur. The pressure in the system is initially high, due to the elasticity of the pipes, giving you a spurt of water. Once the flow starts, the pressure and flow drop suddenly after the pipes release this stored energy. When the threshold is reached, the pump kicks on, causing the pressure and flow to increase, casing the flow and pressure to surge. If the flow rate through the faucet or shower head is insufficient to keep the pressure from rising above the pump cut off threshold, the pump will stop, until a moment later when the pressure drops causing the pump to start again. This rapid cycling of the pump wears out the system's components quickly.
The pressure tank also provides stable flow which may otherwise lag during pump startup. When you open a faucet, the time between the initiation of flow and a drop in pressure sufficient to trigger the pump would be noticeable in the output pressure and flow rate. If the flow rate is sufficiently restricted, say by only opening the faucet part way or by a restrictive shower head, a surging effect can occur. The pressure in the system is initially high, due to the elasticity of the pipes, giving you a spurt of water. Once the flow starts, the pressure and flow drop suddenly after the pipes release this stored energy. When the threshold is reached, the pump kicks on, causing the pressure and flow to increase, casing the flow and pressure to surge. If the flow rate through the faucet or shower head is insufficient to keep the pressure from rising above the pump cut off threshold, the pump will stop, until a moment later when the pressure drops causing the pump to start again. This rapid cycling of the pump wears out the system's components quickly.