feeding membrane with waste water

[Daftoldgit]

I have set up 2 100gpd membranes with the waste water from membrane 1 feeding the input of membrane 2.
Should the flow restrictor, which is after membrane 2, be the normal size for a 100gpd membrane, or sized for 200gpd as there are two of them? or somewhere in between? I have 800 restrictor at the moment, it makes about 3.5 to 1 waste ratio which seems a bit high?

 

[spruce]

Why not change the restrictor to a 1/4" gate valve so you can adjust the waste yourself? @Daftoldgit

The trouble with these restrictors is that they come preset. The specific one I had for my 450gpd was 3 waste to 1 pure. It worked for many years, but I did waste a lot of water.

 

[francie]

I have set up 2 100gpd membranes with the waste water from membrane 1 feeding the input of membrane 2.
Should the flow restrictor, which is after membrane 2, be the normal size for a 100gpd membrane, or sized for 200gpd as there are two of them? or somewhere in between? I have 800 restrictor at the moment, it makes about 3.5 to 1 waste ratio which seems a bit high?

Would that not wreck your second membrane?
How come your doing that?

 

[Daftoldgit]

Cheers Spruce, I didnt I didn't know there was such a thing a thing as a 1/4 gate valve, is it something available from RO suppliers?
Francie it's supposed to save water as the waste gets used to feed membrane 2 instead of going straight down the drain or that's the theory anyway.

 

[ched999uk]

Cheers Spruce, I didnt I didn't know there was such a thing a thing as a 1/4 gate valve, is it something available from RO suppliers?
Francie it's supposed to save water as the waste gets used to feed membrane 2 instead of going straight down the drain or that's the theory anyway.

You can get a john guest valve with 1/4 push fits from Amazon for £6

 

[Daftoldgit]

You can get a john guest valve with 1/4 push fits from Amazon for £6

Nice one, I'll get one ordered and give it a try, cheers!

 

[spruce]

Would that not wreck your second membrane?
How come your doing that?

You are correct, as the second membrane takes a higher TDS. Some suppliers assemble their r/o's like this.

Ro-Man.com used to have a schematic on their website many years ago showing 3 ways to connect a 3 membraned r/o up.

1st: The prefiltered tap water split 3 ways and fed into each membrane. All pure pipes were joined together to storage and all waste outlets were joined together, then restrictor and then drain. This makes total sense to me and the way my 450gpd r/o was plumbed.

2nd: The prefiltered tap water was split into 2 and fed into the first 2 membranes. The wastes of these 2 membranes were joined together and fed into the inlet of the 3rd membrane.

3rd: The prefiltered tap water was fed into the first membrane only. The waste from the first membrane was fed into the second membrane and the waste from the second membrane was fed into the 3rd membrane.

Apparently method 2 and 3 was a way of saving water. These membranes aren't all that expensive to replace. Saving water at the expense of premature membrane longevity could make economic sense.

If you count up the number of Tee pieces you need on the first method, you will see you need a lot more than say the 3rd method. Was this a way of a supplier being able to reduce costs to make his offering more cost-effective and price attractive, or was it to increase his profit margin?

 

[Skxawng]

Mine is from ro-man about 12 years ago and is set up as scenario 3 as above. I've always wondered why I get better pure to waste ratio than some and now I know why, thanks ?

 

[spruce]

Mine is from ro-man about 12 years ago and is set up as scenario 3 as above. I've always wondered why I get better pure to waste ratio than some and now I know why, thanks ?

Mine came from the late Peter Fogwill back in 2003/4, and he connected it up as per method 1.

One of the other local lads bought his last r/o from another supplier and his was connected up as per method 2.

 

[spruce]

Nice one, I'll get one ordered and give it a try, cheers!

Please always make sure you never fully close this valve when producing water. In time, it will also wear, so expect to have to close it fractionally more over time and for it not to last forever.

 

[Iron Giant]

Nice one, I'll get one ordered and give it a try, cheers!

As you're in Wiltshire and in a hard water area your production is going slow using x2 100gpd membranes you'd be better off with a 40/40

 

[spruce]

As you're in Wiltshire and in a hard water area your production is going slow using x2 100gpd membranes you'd be better off with a 40/40

When we first went wfp there was a window cleaner who had a DIY window cleaning website. I can't remember his name or that of his site.

He processed water with a single 50 gpd membrane. His r/o ran 24/7. It never stopped. I never understood how he could produce enough water to clean windows.

 

[Iron Giant]

When we first went wfp there was a window cleaner who had a DIY window cleaning website. I can't remember his name or that of his site.

He processed water with a single 50 gpd membrane. His r/o ran 24/7. It never stopped. I never understood how he could produce enough water to clean windows.

I wouldn't have either, it takes me around 9 hours to produce 350ltrs with my 450gpd R/O and that's year round near enough, sometimes I have to use my booster pump to up production to produce the water I need for each day

 

[Iron Giant]

I have set up 2 100gpd membranes with the waste water from membrane 1 feeding the input of membrane 2.
Should the flow restrictor, which is after membrane 2, be the normal size for a 100gpd membrane, or sized for 200gpd as there are two of them? or somewhere in between? I have 800 restrictor at the moment, it makes about 3.5 to 1 waste ratio which seems a bit high?

No mention of pre-filters, you do have a sediment filter and a carbon filter before the first membrane?

 

[Daftoldgit]

Iron Giant - Yes I have a filter, a combined one
We do have hard water, it's about 300.. I seem to make enough water, I probably get through less than some do in a day.. I only use 250 litres a day max.
Spruce - I'll fix the tap in position somehow just to be on the safe side

 

[Iron Giant]

Iron Giant - Yes I have a filter, a combined one
We do have hard water, it's about 300.. I seem to make enough water, I probably get through less than some do in a day.. I only use 250 litres a day max.
Spruce - I'll fix the tap in position somehow just to be on the safe side

Personally through advice from @spruce some years ago, I'd have a white sediment filter in a clear housing this allows you to see if you have sediment issues at a glance I switched to wfp 14 years ago and only started have issues with sediment around 3 years ago I think it was at one point I was changing my white sediment filter every 3-4 weeks the sediment filter will help preserve the lifespan of your combined sediment & carbon filter of which I have both on my set up.

 

[spruce]

Personally through advice from @spruce some years ago, I'd have a white sediment filter in a clear housing this allows you to see if you have sediment issues at a glance I switched to wfp 14 years ago and only started have issues with sediment around 3 years ago I think it was at one point I was changing my white sediment filter every 3-4 weeks the sediment filter will help preserve the lifespan of your combined sediment & carbon filter of which I have both on my set up.

Again, this is exactly how Peter Fogwill used to supply his small r/o's. The first sediment filter had a clear bowl - the others weren't. It didn't take me long to realise this was very helpful to see the state of the filter at a glance. I could never understand why some other r/o suppliers at the time sold their units with non see through sediment filter bowls.

I still see a couple of suppliers selling complete 4040 system with non-clear prefilter bowls. Here is an example:

https://www.ebay.co.uk/itm/363865133147?hash=item54b80d505b:g:p6AAAOSw2NZin2~b

When I assembled my own 4040 10 years ago, I ordered 2 x 20" prefilters with clear housings.
Now I can keep an eye on both at a glance. I have never had an issue with the carbon block filter, so in hindsight didn't need a clear bowl. If I were setting up another 4040 now, I would still go for 20" prefilters with clear bowls.

 

[Daftoldgit]

I think I have some unused sediment filters stashed away somewhere, I'll have a look, as the sediment filter housing is unused at the moment (it's not transparent though)
The valves and fittings have been dispached! I orderd 2, one for restricting, one for flushing, I plan to run them parallel, when I fit them and experimented a bit. I'll let you know how it works out. Thanks for the advice!

 

[spruce]

I think I have some unused sediment filters stashed away somewhere, I'll have a look, as the sediment filter housing is unused at the moment (it's not transparent though)
The valves and fittings have been dispached! I orderd 2, one for restricting, one for flushing, I plan to run them parallel, when I fit them and experimented a bit. I'll let you know how it works out. Thanks for the advice!

In all the years we have been wfp it's only this past year that my sediment filter has lasted as long as the carbon block.
It's only been on the last change that my sediment filter looked new but with a slight stain.

Over the years, every window cleaner living in our area has experienced the same with their water as I have.

 

[Daftoldgit]

Ok so I played around with it this evening, so I can get the waste water ratio right down now, which is good as I'm on a meter. I was expecting the pure output to rise as the waste ratio decreased, I was surprised to find that the pure output remains the same whatever the ratio.

 

[doug atkinson]

It will do but you will find your ppm will have increased a bit.