[combat1]

Upgraded my membranes about 3 months ago to two 150gpd membranes, fitted a 150gpd flow restrictor and a Gardiners new type pre filter.
My production rate has dramatically slowed down, takes over 12 hours to make 150 litres, before took half that time.
I do have a booster pump fitted and wondered whether that was now not right for the new membranes

[andyM]

Out of interest what size membranes were you using before you upgraded to the 150 gpd ones?

[combat1]

Hi Andy, I started out with a 100gpd RO and bought an upgrade kit which added another 100gpd membrane, When the time came to change the membranes I upped to two 150gpd membranes.

[8weekly]

Check that the prefilters are in the right order.

[pure tech]

I replaced 3 x 100gpd membranes recently (purchased from Gardiners) and am having the same problem.
The original membranes when new produced at 1:1 product to waste and took about 35 minutes for 20 litres and the new ones take about 60 minutes with twice as much waste as product although the flow restrictor is working ok as a new one made no difference. The good news is that I am getting 001ppm before resin out of 100ppm  tap water.
I wonder if the membrane specs are different to the originals?

[Spruce]

I replaced 3 x 100gpd membranes recently (purchased from Gardiners) and am having the same problem.
The original membranes when new produced at 1:1 product to waste and took about 35 minutes for 20 litres and the new ones take about 60 minutes with twice as much waste as product although the flow restrictor is working ok as a new one made no difference. The good news is that I am getting 001ppm before resin out of 100ppm  tap water.
I wonder if the membrane specs are different to the originals?

I think that you have the answer.

Combat has fitted new membranes with the right restrictor. If it's a cartridge type that plugs into the waste line, then it has a nozzle size that restricts the flow that suits those membranes. If he measure his waste to pure ratio, he will find that he produces about 3 times more waste than pure in the same time (3 litres waste to 1 litre pure.)  

This is the right ratio for RoMan type r/o's. In the early days, there was an optional restrictor of 5 : 1 that was meant for water with a very high TDS (very hard water.)
It could have been that a different restrictor was fitted previously, either in error or intentionally that was for a smaller membrane. In this case the waste would have then 'throttled' back more, forcing more water through the membrane. The result would be more pure, but at a lower purity. The long term effect is that the membrane won't last as long.

I know of a cleaner who has a restrictor tap on his waste and he adjusts that so he gets roughly the same waste to pure (1:1) so its possible to do it. If you are on a water meter, then you need to balance the need to reduce the water waste (waste water costs money) against that cost of replacing membranes that have failed prematurely plus reduced resin costs (producing purier water).

Hopefully others may read this pure to waste ratio discussion and comment with their experiences. If not, you may have to start another thread regarding RoMan type r/o restrictors.

I have always found Doug at dagua.co.uk to be very helpful regarding matters such as this.

[Spruce]

Upgraded my membranes about 3 months ago to two 150gpd membranes, fitted a 150gpd flow restrictor and a Gardiners new type pre filter.
My production rate has dramatically slowed down, takes over 12 hours to make 150 litres, before took half that time.
I do have a booster pump fitted and wondered whether that was now not right for the new membranes

Hi Combat1.

If this has started to occur during the last 3 months, then you have to focus on the new Gardiner prefilter. Originally it was suggested that this was an all in one filter, so you could throw your sediment prefilter away.

There are some areas where our water supply is high in sediment as it is in our case. I have a different long life carbon block filter in at the moment and even with a sediment filter i'm taking the prefilters off every 3 months as they are clogging up. I'm back flushing my c/b filter like we did with our swimming pool filters overseas then take it out and hose the outside sediment off.

If this low production rate became an issue the moment you changed the membranes then it isn't a prefilter issue. In this weather with warmer water, you should be producing water much quicker. This could be a restrictor issue. The way to check this is to run the waste and the pure for a length of time and then measure them. I saw a photo of a person who had run his waste into an empty 25 litre container and his pure into another. At a glance he could see what was happening.

[combat1]

Hi All, thanks for your input. getting worse just taken twenty four hours to make around two hundred litres!
Still that's Monday sorted.
Maybe my membranes are clogging up and that makes me wonder about the new pre filter which I fitted. The original instructions were to leave the sediment filter empty and just fit the new style filter in the other chamber, now I notice that the website recommends fitting a 10 micron sediment pre filter for maximising the life of the new filter. The new one has done around 25,000 litres and is supposed to have a life of 75,000 litres.
Will have to buy water after Monday until I can sort it out.
Luckily I bought the membranes and flow restrictor from Daqua so will email Doug to see what he thinks.
Will let you know guys what happens! thanks for your help.

[Alex Gardiner]

As has been said there are two things to check here.

1.Which new pre-filter did you buy? If it is the Fibredyne CFBC then in high non-dissolved sediment areas (not high TDS necessarily) it may have clogged up. We recommend that these are fitted with a 5 micron pre-sediment filter to prevent this if you are in a high non-dissolved sediment area.

If it is the Fibredyne CFB-Plus then it should be OK as these have a less fine micron filter in them which does not clog up anywhere as easily. The quickest way to check if it is the pre-filter is to remove the pre-filter and replace with another one. If this cures it then this is the issue. If it does not cure it then you need to look at point 2

2. You fitted new 150gpd membranes. Did you have these type before or were you using 100gpd membranes previously?

If you have just upgraded to these and you live in a high calcium, limescale and mineral area the new membranes may well be calcifying/limescaling up. Does your kettle limescale up very quickly? If so this may be the reason. The 150gpd membranes whilst producing more water are more prone to clogging and limesacale than their 100gpd counterparts. This is because the membrane layers are more tightly packed to achieve higher production rates - the downside is it is a lot easier for them to limescale and clog. This can happen in as little time as 2 weeks. If you have this type of water and want to use these membranes then you will need some kind of softener first.

[combat1]

Thanks Alex, the advice is as usual most helpful. I will check all and maybe have to revert to the old membrane rating if that is the problem. Many thanks, Chris.

[pure tech]

A question that perhaps Alex or Spruce may be able to answer:
Would a JG push fit on/off ball valve (tap) be a suitable substitute for the existing flow restrictor.
This would enable the the waste to be adjusted to the suitable ratio.
Or is a flow restrictor more complicated than a tap?

[Alex Gardiner]

A question that perhaps Alex or Spruce may be able to answer:
Would a JG push fit on/off ball valve (tap) be a suitable substitute for the existing flow restrictor.
This would enable the the waste to be adjusted to the suitable ratio.
Or is a flow restrictor more complicated than a tap?

You can certainly use these for such a purpose. They can be quite hard to adjust accurately so if you have two of them in a loop, one of them is used to flush and the other to set the waste ratio.

[combat1]

Hi all, The RO is now working fine thanks, changed the flow restrictor and am now back in production.
Out of interest I have just done a waste to pure test in two twenty five litre barrels. 25 litres of waste to 10 litres of pure water.
Thanks all for your help.

[Spruce]

Hi all, The RO is now working fine thanks, changed the flow restrictor and am now back in production.
Out of interest I have just done a waste to pure test in two twenty five litre barrels. 25 litres of waste to 10 litres of pure water.
Thanks all for your help.

I'm glad you got it sorted. Its always good to hear the solution to a problem so we can put this in our memory for next time. The pure to waste ratio you have is fine IMHO.

[pure tech]

Hi all, The RO is now working fine thanks, changed the flow restrictor and am now back in production.
Out of interest I have just done a waste to pure test in two twenty five litre barrels. 25 litres of waste to 10 litres of pure water.
Thanks all for your help.

Good to hear you have it sorted.
I am interested to know how long it now takes to produce 150 litres.
I actually measured my pure/waste ratio and it works out at 10 litres of waste to 7 litres of pure, so not as bad as I thought it was although everything is still much slower with these new membranes.
Oh, and thanks Alex for that advice.

[a900]

I was wondering if the booster pump cant cope with the extra flow of new membranes. And because of the increase in membrane the result without more flow is more water out of waste rather than more overall pure water.

Not sure if that is making much sense.

I upgraded my ro from 300gpd to 450gpd and found my water pressure to be to low so brought a booster pump off ebay only to find it would not flow enough water to produce the correct pressure, making my production speed poor. If I closed off the waste flow restrictor it would produce faster but tds would then rise.

I have since put a pump capable of the job on.

[combat1]

Hi Pure Tech, just produced about 160 litres in five hours, don't know whether that's a good time or not? perhaps someone will be able to tell us.

[Alex Gardiner]

Hi Pure Tech, just produced about 160 litres in five hours, don't know whether that's a good time or not? perhaps someone will be able to tell us.

That sounds pretty good for a 300gpd system. This equates to about 768 litres in 24 hours which is about what I used to get from my 300gpd on 105psi input.