[andyralph]

hi all swaping my merlin for a 4040 or 4021 from daqua any ideas which one his best and best membrane to have hf5 or hf4 i use a booster pump as my pressure is not great thanks andy

[CleanClear]

Andy a 4040 is 40 inches long and a 4021 is 20 inches long. The longer one produces water faster. There is no best, its just how much water do you need filled in a time frame.
 As for HF4 or HF5 well (i hope i got this right way round  ) the HF5 is a low pressure membrane. IN reality that equates to the fact it can work at about 20 PSI lower than a HF4, it will still need about 80 PSI to work to its best. That said i'd go with the standard one, which is cheaper also i think. I can't see any logic in pumping a system and then using a low pressure membrane for the high pressure you now have?

[dave0123]

ive had both 40 inch and a now have a 21 inch membrane (4021) using a hf5 membrane very low pressure i have of around 25 psi .. i have  a booster pump which i only use it at 60 psi and brings my tds down at the moment to 8 ppm. Ring June explain your low pressure to her she may ask what your water pressure is she will advise which membrane is best for you.. i have done this myself and went with a smaller membrane after her recommendation for it.

the 40 inch membrane never got anywhere near this lucky if i got it below 20. the smaller membrane will produce water slower obviously but its not that much slower if  you have a static system it probably wont be a problem because you could leave it on.. but it depends what you want at the end of the day.

The smaller membrane i am using now is going to save me loads on resin so i am more than happy with it... they cope a little better if you have low water pressure compared to the 40 inch membranes

[dave0123]

What many window cleaners may not realise is that reverse osmosis membranes (with the exception of small residential membranes) are not designed to work off tap pressure. Even the much loved HF5-4040 "Ultra Low Pressure" membrane is designed to be used in engineered reverse osmosis systems running at about 80 psi. Normal Extra low energy membarnes are designed to work at about 100 psi. If you study the data sheets you will also note that the manufacturers recomend that they should be run with 85% waste. This is the reason why we seldom reach the advertised 99% or 98.5% rejection rates nor the high flow rates shown on the data sheets.

[Clever Forum Name]

Great advice, but if you are buying from Aqua ask them They will give you all the info you need.

I am experimenting with waste ro water at the moment. Kinda like recycling but in a different way.