[Mike55]

Hi there.
I'm helping another windie out and wonder if anyone could help me out with trying to discover why the tds is rising following a change of membrane a month ago.

He has a fitted brodex system in the van (20" RO membrane) and replaced the membrane about a month ago.  The tds output was around 13 initially, but has already risen to 24, despite regular flushing.

Could it be that the psi from his water mains is too low and this would cause a quick rise in tds?  It is a hf4 membrane so designed for higher pressure and at present he doesn't use a booster pump.  He has ordered a pressure gauge to check the psi reading.

Is it simply down to the fact that he needs a booster pump?

The one that brodex sell is around £450 so would there be a suitable alternative for less money?

Any help appreciated. 

[dave0123]

Open the waste water pipe more so there's a lot going to drain, then see if it starts to go down over time.

[Mike55]

I don't think it's down to the waste.  He has told me that when he flushes the system he doesn't produce any product water at all so I presume the waste is fully open?

[R.C Property]

That's right, when he is producing pure water might need to open the waste tap more to slow the pure water down a bit.

Maybe the prefilters need changing?

[Mike #1]

Yup pre-filters are the first thing to change long before RO membranes everything needs to checked piece by piece .

To ensure everything is contaminant free .

Low water pressure will not affect TDS ,  to much water pressure will have an adverse affect as the RO unit has to process the water far quicker which will reduce the life of the membrane .


Dont you think its strange that despite this forum having loads of windys on who use wfp hardly any of us know much about the filtration process . Mike

[R.C Property]

Dont you think its strange that despite this forum having loads of windys on who use wfp hardly any of us know much about the filtration process . Mike

+1 on that one, people just thinking it's easy to do, just add water so to say.
But saying that I don't use a 4040 so can only give limited advice on them, the basics are roughly the same in all ro's

[Mike55]

Thanks guys.

To be fair I've not actually seen his set up but I know he changes his prefilter (Brodex only use one - carbon) every three months and flushes regular.

I will have a look at his flush valve to make sure he is setting it at optimum.  I probably should have done this first thinking about it now  :

[SPE]

I'm helping another windie out and wonder if anyone could help me out with trying to discover why the tds is rising following a change of membrane a month ago.

about the same time it started getting colder perhaps ? an ro's performance is affected by temperature,
maybe (only my guess) this cold weather has something to do with it.

[home6442]

You need a sediment filter or your carbon filter wont last long.
Sediment will block a carbon filter very quickly.

[dave0123]

Low water pressure will not affect TDS ,  to much water pressure will have an adverse affect as the RO unit has to process the water far quicker which will reduce the life of the membrane .

Yes it will affect the TDS, the RO membrane is designed to work best with a pressure of 80psi if you pump it in at this pressure it will effect the TDS dramaticly by reducing it(if you have low pressure). But this will only work if the flow from your water tap produces enough water per min. Flow and pressure are two diffrent things.


Speak to June at GAPS water about it.

I had the same problem about three years ago it started off at 13 and ended up at 30 the reason being is because the pump didn't have enough water being fed into it to bring the tds down. June at gaps called it starving the RO membrane. But if i opened the tap to about 50% waste 50% pure it brought it right down... the pressure is 62psi.. and thats what they recommended was the best option was the opening the tap for me.

At first i was running it without a pump it simply wasn't a viable option. June at gaps had a water diagram print out of all my details water pressure/water intake/ and the amount it was producing.. in the end it was come down over time but its never under 10ppm.

You can also re enter some of your pre-filtered water if that makes sense it may help if you don't have enough water flow per min.

[richard jagger]

If you prefilter are gone the water pressure will drop as the filter get dlocked with solids it will not have an effect on the membrane if its a high pressure membrane and the pressure is low that will have an effect on the quality of the pure and with colder weather the volume of  production water will drop. My first choice will be weather with cold water flowing slower and this will effect TDS on a high pressure membrane. A Booster pump will have a positive effect on the TDS.