Question: 

 

I have installed a new RO membrane but the TDS is coming out high?

 

Answer: 
 
There are a few things that can result in a high TDS coming from a new RO Membrane.
 
  • New membranes can take a while to hydrate properly and flush through. It is common for the RO product water to be initially high but this should quickly decrease after an hour or so of running. We reccomend that this inital product water is disposed off.
  • The incoming water pressure may be low and not putting enough pressure on the membrane, typicaly a mains water pressure of 50 psi up to around 80 PSI is needed for best performance. Low water pressure can lead to TDS creep across the membrane and poor efficiency. In low water pressure situations it is recommended to use a booster pump.
  • Incorrect, broken or blocked flow restrictor. The flow restrictor needs to provide the correct rejection rate for the membrane, if the flow restrictor size is incorrect this will effect performance and can damage the membrane, for example a 50 Gallon per day RO unit will need a 300 ml/min flow restrictor. When changing the membrane we recommend changing the flow restrictor as they can block over time, especially in hard water areas.
  •  If new pre-filters were installed at the same time and then not flushed before connecting to the membrane carbon dust liberated from the carbon filter may have been forced into the membrane upsetting TDS readings.
  • The rubber gasket on the body of the membrane or one of the o-rings that seal it at the bottom end of the membrane housing may have been pinched or damaged during installation. Carefully remove the membrane and check these before inserting it back in to place, making sure it is pushed all the way home.