RO membrane questions.

[Delabrum]

I’ve been running a 600 GPD system for almost a couple of months now. I normally get 40 litres of pure per hour, but in the last week, it’s dropped to around 34/35 litres per hour. I’m still pretty new to this WFP lark, and I misunderstood how regularly I need to change the pre filters - to cut a long story short I thought they would need changing every 6-8 weeks, but it turns out they need changing every 3-4 weeks. So in other words I’ve been running the pre filters for almost a month past the recommended usage capacity. Doh. 
 

My tds from the tap is about 120 and the RO pre resin is reading 2, so my rejection rate is 98-99%, which implies to me that the RO isn’t knackered. But could the reason my production rate has slowed a bit be down to damaging the RO membranes? If so, will my current output stabilize at 34/35 litres per hour if I change the pre filters more regularly?

I know 5 or 6 litres less per hour doesn’t sound like much, but if my production continues to slow I’ll run into problems making enough water for our little team. 
 

Thanks guys.

 

[Baldmonkey]

I’ve been running a 600 GPD system for almost a couple of months now. I normally get 40 litres of pure per hour, but in the last week, it’s dropped to around 34/35 litres per hour. I’m still pretty new to this WFP lark, and I misunderstood how regularly I need to change the pre filters - to cut a long story short I thought they would need changing every 6-8 weeks, but it turns out they need changing every 3-4 weeks. So in other words I’ve been running the pre filters for almost a month past the recommended usage capacity. Doh. 
 

My tds from the tap is about 120 and the RO pre resin is reading 2, so my rejection rate is 98-99%, which implies to me that the RO isn’t knackered. But could the reason my production rate has slowed a bit be down to damaging the RO membranes? If so, will my current output stabilize at 34/35 litres per hour if I change the pre filters more regularly?

I know 5 or 6 litres less per hour doesn’t sound like much, but if my production continues to slow I’ll run into problems making enough water for our little team. 
 

Thanks guys.

In your membrane there is a coiled up sieve for want of a better phrase. The sieve allows water molecules through and traps the heavier minerals from getting through... What you have to do is flush the membrane preferably everytime you produce by opening the waste tap full for around five minutes to flush everything out from the sieve so to speak 

 

[Delabrum]

In your membrane there is a coiled up sieve for want of a better phrase. The sieve allows water molecules through and traps the heavier minerals from getting through... What you have to do is flush the membrane preferably everytime you produce by opening the waste tap full for around five minutes to flush everything out from the sieve so to speak 

Yup thanks, I’ve been flushing the membranes. Granted not every time I produce, maybe once or twice a week for 5-10 minutes. Should I maybe give it a really long flush and see if that helps? Can giving your membranes a really long flush do any damage or does it not make any difference?

 

[Baldmonkey]

Yup thanks, I’ve been flushing the membranes. Granted not every time I produce, maybe once or twice a week for 5-10 minutes. Should I maybe give it a really long flush and see if that helps? Can giving your membranes a really long flush do any damage or does it not make any difference?

No you won't do any damage flushing for a long while, some membrane manufacturers state to flush for hours on some membranes. 

 

[Delabrum]

No you won't do any damage flushing for a long while, some membrane manufacturers state to flush for hours on some membranes. 

Ok cool, thanks. I will give that a try tomorrow after work and see what happens. Do you think my membranes are maybe still in good condition then?

 

[Baldmonkey]

Ok cool, thanks. I will give that a try tomorrow after work and see what happens. Do you think my membranes are maybe still in good condition then?

If they are still producing a good ratio you should be fine, I put a post on not long ago about clear sediment filters etc for ease of seeing when they needed changing, check it out

 

[Delabrum]

If they are still producing a good ratio you should be fine, I put a post on not long ago about clear sediment filters etc for ease of seeing when they needed changing, check it out

My ratio is still about the same as when I first setup - it’s about 3 parts waste to 1 part pure. Put it this way, I’m glad I’m not on a water meter!

I’ll be sure to check that out. Thanks.

 

[spruce]

My ratio is still about the same as when I first setup - it’s about 3 parts waste to 1 part pure. Put it this way, I’m glad I’m not on a water meter!

I’ll be sure to check that out. Thanks.

Prefilters are very important.

For every 1 litre of pure you are using 4 liters of tap water at your ratio. If your carbon block filter (the second one in) only has a service life of 6000 liters then its not going to be long before that filter needs replacing. Hence the reason why I use a Fiberdyne carbon block as they last longer. (Your carbon filter service life includes all the water going through your r/o - waste and pure.)

Of course the actual service life of your carbon block is down to how much chlorine is in your water. But as we don't know the only thing we can do is follow the filter change recommendations of the filter manufacturers.

With a low tap water tds of 120ppm you should be able to run at 60 waste to 40 pure which will extend the intervals between prefilter changing.

In Saltburn and surrounding areas we are prone to get a lot of sediment in our water supply. In time the sediment filter (the first inline) will become blocked with it. In times past I replaced a sediment filter twice before replacing both when the carbon block filter was due for replacement.

 

[ShropsWindowCleaner]

How do you know when a sediment filter becomes blocked? I have recently installed one. I can visually inspect it, but will it simply not allow water through once blocked?

Prefilters are very important.

For every 1 litre of pure you are using 4 liters of tap water at your ratio. If your carbon block filter (the second one in) only has a service life of 6000 liters then its not going to be long before that filter needs replacing. Hence the reason why I use a Fiberdyne carbon block as they last longer. (Your carbon filter service life includes all the water going through your r/o - waste and pure.)

Of course the actual service life of your carbon block is down to how much chlorine is in your water. But as we don't know the only thing we can do is follow the filter change recommendations of the filter manufacturers.

With a low tap water tds of 120ppm you should be able to run at 60 waste to 40 pure which will extend the intervals between prefilter changing.

In Saltburn and surrounding areas we are prone to get a lot of sediment in our water supply. In time the sediment filter (the first inline) will become blocked with it. In times past I replaced a sediment filter twice before replacing both when the carbon block filter was due for replacement.

 

[Baldmonkey]

How do you know when a sediment filter becomes blocked? I have recently installed one. I can visually inspect it, but will it simply not allow water through once blocked?

https://windowcleaningforums.co.uk/topic/33023-how-do-you-know-when-to-change-your-sediment-filter-heres-how-ent/?tab=comments#comment-464566

 

[Delabrum]

Prefilters are very important.

For every 1 litre of pure you are using 4 liters of tap water at your ratio. If your carbon block filter (the second one in) only has a service life of 6000 liters then its not going to be long before that filter needs replacing. Hence the reason why I use a Fiberdyne carbon block as they last longer. (Your carbon filter service life includes all the water going through your r/o - waste and pure.)

Of course the actual service life of your carbon block is down to how much chlorine is in your water. But as we don't know the only thing we can do is follow the filter change recommendations of the filter manufacturers.

With a low tap water tds of 120ppm you should be able to run at 60 waste to 40 pure which will extend the intervals between prefilter changing.

In Saltburn and surrounding areas we are prone to get a lot of sediment in our water supply. In time the sediment filter (the first inline) will become blocked with it. In times past I replaced a sediment filter twice before replacing both when the carbon block filter was due for replacement.

I believe my GAC and carbon block both have service lives of about 12,000 litres. I’m in Marske, and as you say, the sediment filter was pretty gunky when I replaced it.

So when you say I should be able to run at 60 waste to 40 pure, is there a way I can actually achieve this? I’m guessing a booster pump?

Also can you recommend the Fibredyne carbon block that you use? It will probably be more cost effective long term to buy filters that last a lot longer, even if they’re more expensive.

Another quick question, have I actually got my pre filters in the correct order? I have sediment filter first, then GAC then the carbon block. Should I switch the carbon block and GAC?

 

[spruce]

I believe my GAC and carbon block both have service lives of about 12,000 litres. I’m in Marske, and as you say, the sediment filter was pretty gunky when I replaced it.

So when you say I should be able to run at 60 waste to 40 pure, is there a way I can actually achieve this? I’m guessing a booster pump?

Also can you recommend the Fibredyne carbon block that you use? It will probably be more cost effective long term to buy filters that last a lot longer, even if they’re more expensive.

Another quick question, have I actually got my pre filters in the correct order? I have sediment filter first, then GAC then the carbon block. Should I switch the carbon block and GAC?

Both GAC and the carbon block remove chlorine. The GAC filter is more for the drinks industry.

The achieve a lower waste to pure ratio is to further restrict your water to waste using your waste valve. Some waste valves are restricted to a 3 to 1 ratio. What you need to do is replace that with a small gate valve that you can adjust more finely. The thing with a gate valve is not to shut the waste flow off entirely.

You will need to identify the size of pipe on your waste side ie 1/4" or 3/8"

Here's an example of a 1/4" gate valve.

https://www.ebay.co.uk/itm/Brass-Gate-Valve-Female-BSP-Sizes-1-4-to-2-FREE-DELIVERY/153869795575?_trkparms=ispr%3D1&hash=item23d35ac0f7:g:WJMAAOSw~O1eco9i&amdata=enc%3AAQAFAAACcBaobrjLl8XobRIiIML1V4Imu%2Fn%2BzU5L90Z278x5ickkxGz2ccqatkEnoeekHqhLkeGn39kEOEOunDkx8oSV24knfewLBhWfsH44UMlJJAAsgPf%2BLzj8waxWQHT3%2BqclX42CTl4RUhCny%2FwcCEW3HYntNAv5J8gYFZ%2FPsA2DHAp4Y4fZX7s6chDD8c1fx3estU2nUJWOdFx28XGsEClmYeDa6RskhWddP%2F%2FC6GxC4Zcsp3DzLsFp3HVvrczKmYICstb8PEgDfRs0onAmiSsOVEwMbh52TNj6gLa2XBwZ0LFl5GvPXTmvk%2BAZgVRx7g%2BZEq6JbTyt1ODWH8Y9rn730uERbo84ktOC2h2xJVpJslcnGq7vnC3fS%2B9feN%2BS%2BcaW81wudDKkzwhyHOWcmaC8v4%2BX4fyfzpxI8n6wT8l6guwc6VM9f5%2FPPVFT5dhC0fvsuARS%2BB0CtkliHHg%2FbYSIOwlelzDB06zJ0y7RHbVx5S1uedpulL36ZlZhTZX2ureMGe3pGUlNPNHlvRfW1nl9Qg%2BPlq5yYIV5q9mLpKNIiGw%2Bwk2NI9HXIPOYvr4UPCP2j5PXN25ZUJYfZt73DpyWRvssbt5XXY6%2FAWzJWcPriR%2F%2BTkLGq%2FgVf0Tl96ldKW1ljiGL5Y1KcontKVVeNa5y1sUS2REieazH3RYBm03iFUua5yN8cLDmxhYboRZ8muVsXA3qYPn6PlkoSboNHyj68hFvPaFG%2Fpxnj44nt7Z9Xyy9oi7qnyt4jXneLK4CW2tHgdcKC7Ur1k5R2BQPCmbN%2Frs34OnLafmXhtWBv4SNVR3TcYnIqLo6E3otpMzf7ZAsTA%3D%3D|cksum%3A1538697955757d52009215f14d0b96d9e1f693d9298c|ampid%3APL_CLK|clp%3A2334524

You will need a couple of 1/4" male to 1/4" push fit adaptors.

These guys do a lot of JG fittings

https://www.ebay.co.uk/itm/1-4-John-Guest-Pushfit-Pneumatic-Fittings-For-Water-Air-Vacuum-Filter-Pump-Pipe/322096612681?_trkparms=aid%3D111001%26algo%3DREC.SEED%26ao%3D1%26asc%3D20160908105057%26meid%3Dc23437fed051425395b576467fca9b61%26pid%3D100675%26rk%3D1%26rkt%3D15%26mehot%3Dpp%26sd%3D322096612681%26itm%3D322096612681%26pmt%3D1%26noa%3D1%26pg%3D2380057&_trksid=p2380057.c100675.m4236&_trkparms=pageci%3Abc709aea-f26b-11ea-b142-74dbd1804d5c|parentrq%3A71b4dc5a1740ac3d2a8e83b8fffffcde|iid%3A1

If you look on the post @Baldmonkey linked to you will see a comment from me there as well. I have a pressure gauge on each side of the prefilters. ATM our water pressure is 55psi at the r/o inlet. When the prefilters are new the pressure gauge on the prefilter outlet reads the same.

When that sediment prefilter becomes more and more blocked the pressure gauge after the prefilters will show a reduced pressure. When it drops to 40psi I change the sediment filter. If its close to prefilter change time I replace them both. Last time I looked last week I had 20k to go on the Fiberdyne filter and the pressure is down to 45psi. I'll push it a bit further. I'm also able to close the waste gate slightly to compensate for that sediment filter blocking up.

Many years ago a fellow windie asked me to identify why his production rate was slowing and had finally stopped. His sediment filter was completely clogged up and hardly a drop of water was getting through.Changing prefilters sorted the issue out.

Another has an old Merlin r/o. The first prefilter on that is a Fiberdyne filter which can also be used as a sediment filter - a combination filter. He fitted a separate sediment prefilter housing before his r/o to protect his first filter. Replacing a sediment filter is much cheaper than replacing a Fiberdyne carbon filter because its blocked with sediment.

Our water on this side of Teesside is still terrible, even although its got better over the years.

 

[Delabrum]

Both GAC and the carbon block remove chlorine. The GAC filter is more for the drinks industry.

The achieve a lower waste to pure ratio is to further restrict your water to waste using your waste valve. Some waste valves are restricted to a 3 to 1 ratio. What you need to do is replace that with a small gate valve that you can adjust more finely. The thing with a gate valve is not to shut the waste flow off entirely.

You will need to identify the size of pipe on your waste side ie 1/4" or 3/8"

Here's an example of a 1/4" gate valve.

https://www.ebay.co.uk/itm/Brass-Gate-Valve-Female-BSP-Sizes-1-4-to-2-FREE-DELIVERY/153869795575?_trkparms=ispr%3D1&hash=item23d35ac0f7:g:WJMAAOSw~O1eco9i&amdata=enc%3AAQAFAAACcBaobrjLl8XobRIiIML1V4Imu%2Fn%2BzU5L90Z278x5ickkxGz2ccqatkEnoeekHqhLkeGn39kEOEOunDkx8oSV24knfewLBhWfsH44UMlJJAAsgPf%2BLzj8waxWQHT3%2BqclX42CTl4RUhCny%2FwcCEW3HYntNAv5J8gYFZ%2FPsA2DHAp4Y4fZX7s6chDD8c1fx3estU2nUJWOdFx28XGsEClmYeDa6RskhWddP%2F%2FC6GxC4Zcsp3DzLsFp3HVvrczKmYICstb8PEgDfRs0onAmiSsOVEwMbh52TNj6gLa2XBwZ0LFl5GvPXTmvk%2BAZgVRx7g%2BZEq6JbTyt1ODWH8Y9rn730uERbo84ktOC2h2xJVpJslcnGq7vnC3fS%2B9feN%2BS%2BcaW81wudDKkzwhyHOWcmaC8v4%2BX4fyfzpxI8n6wT8l6guwc6VM9f5%2FPPVFT5dhC0fvsuARS%2BB0CtkliHHg%2FbYSIOwlelzDB06zJ0y7RHbVx5S1uedpulL36ZlZhTZX2ureMGe3pGUlNPNHlvRfW1nl9Qg%2BPlq5yYIV5q9mLpKNIiGw%2Bwk2NI9HXIPOYvr4UPCP2j5PXN25ZUJYfZt73DpyWRvssbt5XXY6%2FAWzJWcPriR%2F%2BTkLGq%2FgVf0Tl96ldKW1ljiGL5Y1KcontKVVeNa5y1sUS2REieazH3RYBm03iFUua5yN8cLDmxhYboRZ8muVsXA3qYPn6PlkoSboNHyj68hFvPaFG%2Fpxnj44nt7Z9Xyy9oi7qnyt4jXneLK4CW2tHgdcKC7Ur1k5R2BQPCmbN%2Frs34OnLafmXhtWBv4SNVR3TcYnIqLo6E3otpMzf7ZAsTA%3D%3D|cksum%3A1538697955757d52009215f14d0b96d9e1f693d9298c|ampid%3APL_CLK|clp%3A2334524

You will need a couple of 1/4" male to 1/4" push fit adaptors.

These guys do a lot of JG fittings

https://www.ebay.co.uk/itm/1-4-John-Guest-Pushfit-Pneumatic-Fittings-For-Water-Air-Vacuum-Filter-Pump-Pipe/322096612681?_trkparms=aid%3D111001%26algo%3DREC.SEED%26ao%3D1%26asc%3D20160908105057%26meid%3Dc23437fed051425395b576467fca9b61%26pid%3D100675%26rk%3D1%26rkt%3D15%26mehot%3Dpp%26sd%3D322096612681%26itm%3D322096612681%26pmt%3D1%26noa%3D1%26pg%3D2380057&_trksid=p2380057.c100675.m4236&_trkparms=pageci%3Abc709aea-f26b-11ea-b142-74dbd1804d5c|parentrq%3A71b4dc5a1740ac3d2a8e83b8fffffcde|iid%3A1

If you look on the post @Baldmonkey linked to you will see a comment from me there as well. I have a pressure gauge on each side of the prefilters. ATM our water pressure is 55psi at the r/o inlet. When the prefilters are new the pressure gauge on the prefilter outlet reads the same.

When that sediment prefilter becomes more and more blocked the pressure gauge after the prefilters will show a reduced pressure. When it drops to 40psi I change the sediment filter. If its close to prefilter change time I replace them both. Last time I looked last week I had 20k to go on the Fiberdyne filter and the pressure is down to 45psi. I'll push it a bit further. I'm also able to close the waste gate slightly to compensate for that sediment filter blocking up.

Many years ago a fellow windie asked me to identify why his production rate was slowing and had finally stopped. His sediment filter was completely clogged up and hardly a drop of water was getting through.Changing prefilters sorted the issue out.

Another has an old Merlin r/o. The first prefilter on that is a Fiberdyne filter which can also be used as a sediment filter - a combination filter. He fitted a separate sediment prefilter housing before his r/o to protect his first filter. Replacing a sediment filter is much cheaper than replacing a Fiberdyne carbon filter because its blocked with sediment.

Our water on this side of Teesside is still terrible, even although its got better over the years.

Thanks for the info. When I’m producing water I have the waste valve fully closed, so I’m guessing I can’t do anything with my ratio other than change that valve as you suggested? 
 

Another query - the flow restrictor on my system is a 3000 ml. That’s what it came with. Correct me if I’m wrong, but is that a little high for a 600 GPD system and could that be contributing to my ratio? Everything I’ve read seems to say you want a 1500/1800 ml flow restrictor for my size system. 

 

[Baldmonkey]

Thanks for the info. When I’m producing water I have the waste valve fully closed, so I’m guessing I can’t do anything with my ratio other than change that valve as you suggested? 
 

Another query - the flow restrictor on my system is a 3000 ml. That’s what it came with. Correct me if I’m wrong, but is that a little high for a 600 GPD system and could that be contributing to my ratio? Everything I’ve read seems to say you want a 1500/1800 ml flow restrictor for my size system. 

NEVER EVER HAVE YOUR WASTE FULLY CLOSED...... you must always allow the membranes to get rid of the solids, you will be doing irreparable damage to your membrane, that's why your production has dropped, because the membrane is clogging up with ****... Start with a 50/50 flow, so make sure your waste has the same flow rate as your pure and adjust as needed..... Minimum is always 50/50

 

[spruce]

Thanks for the info. When I’m producing water I have the waste valve fully closed, so I’m guessing I can’t do anything with my ratio other than change that valve as you suggested? 
 

Another query - the flow restrictor on my system is a 3000 ml. That’s what it came with. Correct me if I’m wrong, but is that a little high for a 600 GPD system and could that be contributing to my ratio? Everything I’ve read seems to say you want a 1500/1800 ml flow restrictor for my size system. 

Perhaps you should get intouch with the suppliers of your r/o and ask them for a restrictor that will give you a better ratio. 60/40 is fine.

 

[Delabrum]

NEVER EVER HAVE YOUR WASTE FULLY CLOSED...... you must always allow the membranes to get rid of the solids, you will be doing irreparable damage to your membrane, that's why your production has dropped, because the membrane is clogging up with ****... Start with a 50/50 flow, so make sure your waste has the same flow rate as your pure and adjust as needed..... Minimum is always 50/50

Ok good to know! Am I missing something here though, when I open the valve my pure to waste ratio decreases - I make more waste to pure. How am I supposed to start with 50/50 when I get 70/30 with the waste fully closed?

 

[Baldmonkey]

Ok good to know! Am I missing something here though, when I open the valve my pure to waste ratio decreases - I make more waste to pure. How am I supposed to start with 50/50 when I get 70/30 with the waste fully closed?

How can you get 70/30 when the waste is fully closed? To get 50/50 you open your waste tap till it gives you the same flow rate as the pure. 

 

[Delabrum]

How can you get 70/30 when the waste is fully closed? To get 50/50 you open your waste tap till it gives you the same flow rate as the pure. 

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!

 

[ched999uk]

I think if you look at the pipe work you have a flow restrictor and a flush bypass. So when you open your tap you allow full flow to waste. When closed the restrictor is throttling the waste flow.

Some people don't have a flow restrictor and just use a tap to limit waste flow. So closing their tap would cut waste flow to zero and damage membrane.

Hope that helps?

 

[Delabrum]

I think if you look at the pipe work you have a flow restrictor and a flush bypass. So when you open your tap you allow full flow to waste. When closed the restrictor is throttling the waste flow.

Some people don't have a flow restrictor and just use a tap to limit waste flow. So closing their tap would cut waste flow to zero and damage membrane.

Hope that helps?

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%?

 

[ched999uk]

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 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.