RO membrane questions.

[spruce]

I think I get it. So are you saying the flow restrictor is what is making my ratio 70/30 with the tap fully open? In that case am I correct in thinking it’s fine to leave the tap fully open on this system?

If so I’m still at a loss to understand why my production has dropped by 10%. I’m gonna give it a super long flush tonight regardless. I don’t think my membranes can be knackered though because my rejection rate is still pushing 99%?

On my old 450GPD I had a combo flush valve and in line restrictor. Here's an example;

https://www.ro-man.com/?product=flush-kit

The on off valve was in the loop. You opened the valve fully to flush. When you closed the valve the water was directed through the restrictor valve. Inside the valve it had a small nozzle which was a preset size which only let through the required amount of water.

There are other valves that have a small hole in the ball which allows a small amount of water threw even when fully closed and then there are valves that completely shut the water off.

When Purefreedom sell a 4040 they drill a small hole through the paddle of the gate valve. The hole is the right size to give the ratio they want.

When I set up my 4040 I also drilled a small hole through the paddle. It was a safety feature in case my son or son in law decided to mess around with it. ATM I still have to adjust the gate valve to get the lowest pure tds by opening the valve.

Gardiner's used to sell John Guest taps. One would completely shut and the other wouldn't.

 

[Delabrum]

IF the tap is connected in parallel to the restrictor then you can close the tap to produce pure and open it to flush. 

Hopefully this image will show how I think your setup is:



As you can see the waste output of the RO goes in on the left and out on the right. IF the tap is closed the waste has to flow through the 550 restrictor. When you open the tap the waste flows round the restrictor through the tap, so no restriction in flow so RO is flushed. When finished flushing close tap and water has to flow through restrictor.

Basically you need some waste to flow to remove the TDS that the RO has removed. The restrictor makes the RO have a pressure across it. 

As for why you are 10% down, that maybe your tap pressure dropped or your filters are partially clogged.

In a big system you could have a pressure gauge each side of the filters. Then you can monitor the pressure drop across filters. When pressure between in and out of filter increases the filter is becoming blocked. 

One thing to remember is the carbon filters might stop removing chlorine before they show a drop in pressure. Chlorine damages RO membranes!!! So ideally you need to know how much tap water enters the system to know when to change the carbon filters and the sediment filter is probably a pressure issue but as their life may vary based on how dirty your water is.

Hopefully that helps. I am never good at a short explanation and hopefully the above is correct.

That’s really helpful, thanks. That’s how my system is setup. Phew, at least I haven’t totally killed the membranes! In fact I just found the manual and it states that after flushing ‘fully close the valve’.

I changed the filters a couple of days ago and the system has a pressure gauge. Pressure is still the same, 45 psi. Even with new filters I’m 10% down on normal. I guess not changing them quick enough has slightly damaged the membranes, is that the only possibility at this point? I’m giving it a mega long flush at the moment, let’s see what happens.

 

[ched999uk]

Glad to help you understand things a little.

One thing I will say is that most membranes really need 70-80psi to run efficiently. Basically a membrane is a very fine filter, so low pressure will make production slow and may produce more waste that running at full pressure - I'm not 100% on that but I believe speed and less waste come from running at a more appropriate pressure.

There are far more experienced and knowledgeable people on here than me. Hopefully they will either confirm what I have said or correct me.

 

[Delabrum]

Glad to help you understand things a little.

One thing I will say is that most membranes really need 70-80psi to run efficiently. Basically a membrane is a very fine filter, so low pressure will make production slow and may produce more waste that running at full pressure - I'm not 100% on that but I believe speed and less waste come from running at a more appropriate pressure.

There are far more experienced and knowledgeable people on here than me. Hopefully they will either confirm what I have said or correct me.

I am seriously considering a booster pump, especially with winter approaching and my system making less pure. It seems that an appropriate pump for a 600 GPD system is harder to find though. Would this pump do the job -

https://www.vyair.com/ro-booster-pump-600gpd-filter-systems.html

 

[ched999uk]

I am seriously considering a booster pump, especially with winter approaching and my system making less pure. It seems that an appropriate pump for a 600 GPD system is harder to find though. Would this pump do the job -

https://www.vyair.com/ro-booster-pump-600gpd-filter-systems.html

As far as I know that would be fine. That pump does say it needs resting every 5 or 6 hrs. When running a pump it's advisable to have a low pressure cut off to protect the pump from running dry (especially if you have a shut off for full tank) . If you are filling a container then it might also be worth having a level switch to shut off flow to your water purifying system so when tank is full it stops processing. If you just shut off the pure to your tank the waste will continue to output water, so using more than necessary.  

 

[doug atkinson]

Reading through your posts what caught my attention was your sediment filter was heavily soiled which often is an induction you may have had dirty water. This will clog up your membranes and reduce your capacity. Another sign is if you open up the cap on the membrane housing and dirty water comes out that’s a sign. Also check your membrane to see if it’s fouled.

 

[Delabrum]

As far as I know that would be fine. That pump does say it needs resting every 5 or 6 hrs. When running a pump it's advisable to have a low pressure cut off to protect the pump from running dry (especially if you have a shut off for full tank) . If you are filling a container then it might also be worth having a level switch to shut off flow to your water purifying system so when tank is full it stops processing. If you just shut off the pure to your tank the waste will continue to output water, so using more than necessary.  

More great advice, thanks again!

Reading through your posts what caught my attention was your sediment filter was heavily soiled which often is an induction you may have had dirty water. This will clog up your membranes and reduce your capacity. Another sign is if you open up the cap on the membrane housing and dirty water comes out that’s a sign. Also check your membrane to see if it’s fouled.

I’ll check my membranes in the morning when I turn the tap off, it’s running at the moment. Thanks, Doug.

Yes the sediment filter was pretty brown and sludgy. Like I said earlier, I hadn’t changed it for the best part of 2 months. Is it not normal for it to be mucky after a couple of months? Also, what exactly do you mean when you say dirty water? I check the tds from my tap relatively often and it’s never been above 130. Can you have a low ish tds from your tap and the water still be full of sediment?

Thanks for all the advice with this guys. There’s so much to keep on top of compared to trad, but 3 months in there’s no chance I’m ever going back ?

 

[Baldmonkey]

This is the tap fully closed, yes? In that position? With the tap in that position I still have way more waste than pure, 70/30 ish. When I very first set it up that’s what I was getting as well. And if I turn it anti clockwise, it produces more waste. I have 45 PSI by the way, maybe I should be looking into a booster?

Apologies if I’m not explaining any of this that well. I’m only a few months in!

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No I didn't understand your system till seeing it, I don't work with flow restricters or bypass, just good old manual waste