# RO system misbehaving



## Hanuman (12 Jun 2022)

Hello,
I've had this RO 5-stage filter for the past 2-3 years. It has worked fine. Had to replace the filters cartridges around 2 times or so. Six months ago I added 2 additional large prefilters (blue ones on the left - sediment + carbon). I also changed the RO membrane from the original 50GPD to a 75GPD.




These are the specs of the booster pump:



Everything has been working smoothly until yesterday when the auto-flush valve started shutting on/off very rapidly.  See video:

Thinking it was the auto-flush valve I bought a new one, installed it, but it just keeps doing the same. So I removed the sediment cartridges and gave them a good rinse thinking they could be dirty and lowering pressure. Didn't solve anything. Then I swapped the RO membrane for an old 50GDP I had laying around thinking perhaps that could be the reason. I could see the pressure on the gauge rise to nearly 80PSI. I think that's due to the RO membrane being old and exhausted and water having hard time passing through it. Anyway, regardless, again it didn't solve the problem. I checked all valves (high pressure, low pressure) and dismantled them to the last bit to make sure they were in good working other. All good. I don't know what else to look for.

What else should I look for? Advise?

Thanks.


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## Stu1407 (12 Jun 2022)

I assume you also swapped the flow restrictor when you increased the size of the membrane? The incorrect size can cause the membrane to foul prematurely.
Worth a quick look. 75 GPD Flow Restrictor


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## Hanuman (12 Jun 2022)

No I did not. Not even sure where I would need to change that. But regardless how would that relate to the auto-flush valve acting like that? I checked TDS yesterday and water is still pretty much as good as the first day. 
In any case I will investigate how to change the flow restrictor to prevent premature aging.


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## Aleman (12 Jun 2022)

The auto flush valve, often incorporates a flow restrictor ... Most commonly 300mlM ... For a 50 to 75GPD this is suitable ... Perhaps 400mlM would be better for a 75GPD, but comes with the cost of increased waste water.

How is your Flush valve wired electrically? ... It should be across the pump (IIRC), so that when the pump switches on the valve opens for 18 seconds the closes, bringing the restrictor into play in the valve body. I'm wondering if it is is a internal pump wiring issue, or perhaps an issue with the HP or LP switches. Swapping to a manual flush valve, allows you to confirm that the rest of the system is working correctly, WRT expected flow rates and operation of the HP and LP switches.


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## Hanuman (12 Jun 2022)

The master piece. It looks something like this...


There is what seems to be a flow restrictor between the pump and the membrane. It's within the tube and looks like this. I didn't check all tubbing so there might be others at strategic locations!!


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## Stu1407 (12 Jun 2022)

Hanuman said:


> No I did not. Not even sure where I would need to change that. But regardless how would that relate to the auto-flush valve acting like that? I checked TDS yesterday and water is still pretty much as good as the first day.
> In any case I will investigate how to change the flow restrictor to prevent premature aging.


Take your point. I have a manual flush anyway but I just wondered if the auto flush was somehow reacting to a blocked membrane but if the TDS is good then that's clearly not the problem.


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## X3NiTH (12 Jun 2022)

I’m no expert on RO systems but it looks like it could be Water Hammer oscillating the valve. What’s the flow from the pump when disconnected before the RO membrane is it pulsing the water? If the pump is used outwith its duty cycle and rest period it could be causing wear on the impeller and may be producing cavitation in the water leading to hammering. Maybe?


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## Hanuman (12 Jun 2022)

X3NiTH said:


> I’m no expert on RO systems but it looks like it could be Water Hammer oscillating the valve. What’s the flow from the pump when disconnected before the RO membrane is it pulsing the water? If the pump is used outwith its duty cycle and rest period it could be causing wear on the inmpellor and may be producing cavitation in the water leading to hammering. Maybe?


I just tested it now. Flow seems rather solid. No oscillation. At least none that I could detect visually or by feeling the flow on my hand. For now I have disconnected the auto-flush valve so that I can produce water without all this shenanigans.  😕


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## Hanuman (12 Jun 2022)

I think I found what could potentially be a flow restrictor on the auto flush valve. That red circle is a screw with a pin. Is that a flow restrictor in your opinion?


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## Aleman (12 Jun 2022)

Could very well be. I've seen similar on AliExpress, some of which are adjustable, and others are not, but look the same


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## X3NiTH (15 Jun 2022)

Make a mark so you are able to reset it back to the original position if you plumb it back in and after adjusting the tension it doesn’t change anything.


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## Kelvin12 (16 Jun 2022)

On the other side of the coin it's not a poor electrical connection.  Loose or dirty connections can cause intermittent supply especially on anything like solenoids.


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## Hanuman (17 Jun 2022)

Kelvin12 said:


> On the other side of the coin it's not a poor electrical connection.  Loose or dirty connections can cause intermittent supply especially on anything like solenoids.


Unfortunately it's not, cables are properly attached. A technician came the other day to put a new auto-flash valve and the same thing happened and he claimed it was normal. I don't think it is since I never heard the filter do that loud noise and I have been the one maintaining it for the past 3 years. I told the company to send a new technician because I am not swallowing that non-sense. He also tested the pump with an external gauge by attaching it to the output of the pump and it was reading what is supposed to be normal pressure, that is ~110PSI.
Technician is coming back on Saturday.


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## Aleman (17 Jun 2022)

I feel your pain  I've just added an autoflush valve to my RO System, and it's not behaving quite as it should either! Either one of the switches is faulty, or I wired it in wrong , although If I go back to the original configuration with the manual flush kit, everything works as it should ... Wiring issue ... Fingers crossed


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## Hanuman (22 Jun 2022)

2nd technician came the other day and claimed it's normal... wonder why I and my family never heard that noise for 3 years... The guy even claimed I can disconnect the auto flush permanently if I don't like the noise 🤨, that's when I invited him to leave as I was not going to take more of that BS.


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## X3NiTH (24 Jun 2022)

Did the technicians ever try swapping out the power supply to all the solenoids connected to the auto flush to see if that may have been the cause of the issue? From what I’ve been reading most of these auto flush valves cycle the solenoid for only a very short time every hour, yours is appearing to cycle out-with that parameter. All the flow charts I’ve read for diagnosing this fault fail to diagnose this fault, frustrating.


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## Hanuman (24 Jun 2022)

X3NiTH said:


> Did the technicians ever try swapping out the power supply to all the solenoids connected to the auto flush to see if that may have been the cause of the issue? From what I’ve been reading most of these auto flush valves cycle the solenoid for only a very short time every hour, yours is appearing to cycle out-with that parameter. All the flow charts I’ve read for diagnosing this fault fail to diagnose this fault, frustrating.


No he didn't and considering how he was looking annoyed by my question I told him to leave.


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## X3NiTH (24 Jun 2022)

Yeah suggesting to remove the Auto Flush entirely isn’t a fix it’s admitting defeat too early, telling you it’s always worked that way when you know it hasn’t is gaslighting you. I’d have kicked him out also!


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## Hanuman (24 Jun 2022)

By swapping out the power supply you mean changing it all together or disconnecting the valves individually from the power supply?


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## X3NiTH (24 Jun 2022)

There’s a situation in the lines between the inlet valve and the auto flush valve, as they are connected electrically together if there is an electrical fault in the inlet solenoid it may be tripping out the auto flush solenoid, if the inlet valve is operating nominally (and it appears to be) then something is causing the auto flush solenoid to go from normally closed to open upon energisation and then back to closed again when it should be energised open for a set period determined by the controller on the auto flush, because you have swapped out this component and the behaviour remained then some other event is causing its failure.

I would remove the inlet solenoid physically and electrically from the system temporarily to see if this changes behaviour in the auto flush, if the behaviour doesn’t change then whatever the power supply is delivering is enough for the inlet but not for the auto flush. If there are other components/devices connected to the same supply then you’ll need to isolate things piece by piece until you discover the issue.

If the state of the auto flush is also determined by water pressure (I haven’t any personal use of one) then something somewhere could be introducing or not abating enough of pressure fluctuation thus triggering the auto flush solenoid.

Somethings not working somewhere and it’s not the device with the issue, it’s a tough one to isolate, real head scratcher!


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## Aleman (25 Jun 2022)

^^^^^^ This ☝️☝️☝️☝️☝️☝️


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