Hi
I am looking for some ideas pls.
We have 3.5 - 4 Bar pressure incoming.
Originally had 2 x HF5 4040 membranes and 2 12" pre filters.
Last year for no reason we started getting only getting 1 ltr every 2 minutes going in the tank @ 20 - 30 PPM
We removed 1 of the HF5 membranes and the flow rate went up to 1 ltr per minute.
Then all of a sudden about a year later our flow rate and dropped back to 1ltr per 2 minutes. We then changed the membrane and it worked fine for a week then suddenly reverted back to 1ltr per 2 minutes.
We was only dumping a very small amount, have we buggered the new membrane or is our PSI to low. Also do we need 2 HF5 membranes?
Ideas will be much appreciated.
Thank you
Further to CleanClear's post, you also need to get your pure to waste ratio right for your system.
With our 4040 with an HF5 membrane we get our best performance (lowest pure ppm from r/o) when the ratio is at 50/50. For us this means that at 50psi input water pressure we get 2lpm of pure and 2 lpm of waste. If I throttle the waste back more, say 30% waste to 70% pure, the tds of the pure rises. If I open the waste gate a little more to say 55 waste to 45 pure then the tds of the pure remains the same. If I open the waste gate further to about 60/40, then the incoming water pressure drops to 40psi and the product water has a higher tds.
Our r/o is plumbed directly into the house plumbing and the flow through our tap and the r/o tested independantly is 13lpm.
It was once stated that to run a 4040 you need to have a minimum of 9lpm from the tap. I think this was in connection with an added booster pump. But as you can see from our r/o, we use 4lpm of tap water to run it. The moment the toilet is flushed or a bath is run, the pressure of water to the r/o drops to virtually nothing. If the wife puts the sprinkler on the lawn when I'm processing water, then I will switch the r/o off until later.
If you have twin membranes, then you will definitely need to know what the flow is from your tap in liters per minute and depending on how you connect it up, in most cases you will need a booster pump. You will also need to be aware of water regulations when using a booster pump as you are not allowed to draw (suck) more than 12lpm through the pipes.
This is why you have to turn a booster pump off when flushing the membrane.
Have you damaged your membrane by restricting your waste? You will need to try to flush and set your ratio up correctly to ascertain it's current situation. There is a warning somewhere that does state that if you close the waste you will damage the membrane but I can't remember where I saw it. My gut feel is that you could well have, especially if you are in an area supplied with water that has a high calcium content. These calcium ions clog the pores of the membrane and could be why your product water is so low.
If you are using a lot of water a day (supplying other cleaners with water for example) then the possible answer is to add an extra storage IBC and link the 2 together. Use a float switch to switch the r/o off when the storage tanks are full.
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