[Ian Lancaster]

Hi all.  Got a weird problem with one of our 300gpd systems (Pure Freedom)

Incoming water pressure is pretty good but we still have a booster just to be sure.  Pressure after prefilters is the same as incoming, so no problem there. 

Production rate is slow to the point of being a fairly quick dribble - took several minutes to fill a half litre container.  Waste water ratio is 2:1 so there's no excess water going to waste.

If it were blocked membranes I would have expected there to be excess waste, and anyway they're only a few months old and been properly flushed from new.

Incoming TDS is 306 and after RO it's 22 so removing about 93% - not as much as it could be but still acceptable performance.

How come it's so slow?  The problem must be in the membranes/housings somewhere as everything is fine up to that stage.

It's got me baffled    
     

[ronaldo]

Alright Ian, had the same problem with ours, was producing quickly but the tds wouldnt come down so changed the filters and still the same.

We then changed the membranes and the tds came down but was only producing at about half as quick as before then after about 2 months back to normal so i just put it down as the new membranes having to sort of wear in if you no what i mean.

[Sapphire Window Cleaning]

It may be because its winter, I have a 500GPD unit and production slows right down in Winter compared to Summer.
Ian where is the unit kept?


Matt

[Matthew JN]

Have you tried flushing the mebranes out by fully opening up the waste control flow valve    Let it run for a half hour or so - then fully turn your valve back to the left for maximum back pressure on membranes to force water through more quickly.

Also having a new sediment pre-filter will help.

[Spruce]

It may be because its winter, I have a 500GPD unit and production slows right down in Winter compared to Summer.
Ian where is the unit kept?


Matt

I agree with Matt. The supply water is just about freezing at the moment. My 450 GPD is very slow when compared to summer. We have to be stricked with ourselves during winter and not waste water. With careful planning we can usually just get through. Peter Fogwill once said that RO membranes should be between 97 - 98% efficient, so yours seem a bit shy of that. I have found that the efficiency of my RO is better in winter, even although much slower. I changed filters yesterday, and could have left the resin vessel until next time as there was plenty good stuff left.
Alway good to buy quality membranes from the States - the Chinese don't make good membranes - RO-man's advise to me once.

[richard jagger]

its sound like your prefilter are blocking for some reason.

[dd]

Try replacing the flush kit, could be it has either suffered some wear or frost damge - about £14 incl. postage from Ro-man.

I have an on/off valve on my system that is a bit similar i had to replace recently.

[Ian Lancaster]

Thanks for all the replies - we have four of these systems but this is the only one that gives us this trouble.  It's not a prefilter problem as the pressure after the prefilters is the same as before them.  I've replaced the restrictor unit with two ball valves so I can accurately set the ratio, so that's not it.  As to slow operation due to cold weather, the other three still work fine in spite of the cold.

Dismantled all three RO housings and associated pipework.  Checked all pipes and unions and replaced all pipes where the union is the screw-on type - these have an integral olive inside the female fitting which grips the pipe and tightens into a tapered socket inside the male fitting - this can restrict the internal diameter of the pipe.  The other fittings (John Guest type) were all OK.

Tested all pipe runs by passing mains pressure water through them - all clear.  Inspected all membrane housings internally - all clear.  Reassembled the unit - no improvement

Here's a question to the technically minded:  each membrane housing has three inlet/outlet fittings.  The outlet for the pure water on all three housings is a right angled fitting which screws into the body of the housing and has the screw thread on the other end to accept the pipe which carries the pure away from the RO to the storage tank/DI cylinder.  Each of these three fittings has a none return valve in it which, when you blow through it, requires a lot of blow to overcome the resistance of the valve.

It seems to me this could be a factor in the loss of flow through the system - why would a none return valve be necessary? As this is the end of the process, there's no chance of contaminated water being drawn back into the system as it goes to an open end.  Has anyone else noticed these valves, or is our system perhaps fitted with them to satisfy some USA legal requirement?

The crunch question: would removing these valves have any adverse effect on the system?  I've thought about it and I can't see why it would, but perhaps someone else knows different?

UPDATE:

Just had a call from Ashley at Pure Freedom who confirms that the non return valves serve no purpose and can safely be removed, so that's my next move.  I'll let you know if it makes any difference!!

[Paul Coleman]

Thanks for all the replies - we have four of these systems but this is the only one that gives us this trouble.  It's not a prefilter problem as the pressure after the prefilters is the same as before them.  I've replaced the restrictor unit with two ball valves so I can accurately set the ratio, so that's not it.  As to slow operation due to cold weather, the other three still work fine in spite of the cold.

Dismantled all three RO housings and associated pipework.  Checked all pipes and unions and replaced all pipes where the union is the screw-on type - these have an integral olive inside the female fitting which grips the pipe and tightens into a tapered socket inside the male fitting - this can restrict the internal diameter of the pipe.  The other fittings (John Guest type) were all OK.

Tested all pipe runs by passing mains pressure water through them - all clear.  Inspected all membrane housings internally - all clear.  Reassembled the unit - no improvement

Here's a question to the technically minded:  each membrane housing has three inlet/outlet fittings.  The outlet for the pure water on all three housings is a right angled fitting which screws into the body of the housing and has the screw thread on the other end to accept the pipe which carries the pure away from the RO to the storage tank/DI cylinder.  Each of these three fittings has a none return valve in it which, when you blow through it, requires a lot of blow to overcome the resistance of the valve.

It seems to me this could be a factor in the loss of flow through the system - why would a none return valve be necessary? As this is the end of the process, there's no chance of contaminated water being drawn back into the system as it goes to an open end.  Has anyone else noticed these valves, or is our system perhaps fitted with them to satisfy some USA legal requirement?

The crunch question: would removing these valves have any adverse effect on the system?  I've thought about it and I can't see why it would, but perhaps someone else knows different?

UPDATE:

Just had a call from Ashley at Pure Freedom who confirms that the non return valves serve no purpose and can safely be removed, so that's my next move.  I'll let you know if it makes any difference!!

I'm intrigued.  I was going to offer a suggestion or two but when I read on, you've already covered the stuff I was thinking about.  I have known scale to build up before but everything I think of is invalidated because your other units are drawing from the same supply.  Assuming you have separate pumps, might it be the pump on the way out.  I've found that they can sometimes play up for quite a while before finally giving up.

EDIT:  You say you've got the pressure monitored so probably not the pump come to think of it.