The following graphic is the result of tests on an RO- Unit, that allowed to disable the built in Permeatepump useing a ball valve. The unit was adjusted to a 4:1 concentrate to product ratio on an emty tank and an open faucet. Feed pressure was 6 bars.
The red curve shows the changes in recovery on riseing tank pressure. To minimize the problem shut off devices are used that allow to produce about 55-75% of line pressure in the storage tank. Note, that in practise the whole storage tank is not used very often. Normally you work out of the top portion of the tank.
The blue curve shows the recovery using the Permeatepump. Here you can see, that the recovery rate does not go down until the Permeatepump shuts the system down close to 100% of line pressure in the tank. This advantage can be used in systems that guarantee that there is always a bigger amount ( > 1 Liter per use) of water used. In household applications a shut off device must be installed. This prevents the production of small amounts each time you draw a cup of water which would cause TDS- Creep.
