[Steven Biggs]

Just after some info . I am gunna have to get some RO as my water has gone from 70 to 200 . I had a merlin about 10 years back and like the simplicity of it . But my only concern is the amount of waste water . Can you shed any light in this . Cheers Gary .

[AuRavelling79]

Two thirds waste to one third pure. Very simple and cheap to run but then - no water meter here.

My tap pressure is high too at between 60 and 70 psi so I don't have another pump to boost it. The Merlin/PRO is not very efficient below about 60 psi.

I also have a separate 10" sediment filter before the unit.

As to capacity I feed me and dan the man and I reckon we do about 3 to 4 days window cleaning per week each as sole operators.

[Steven Biggs]

Cheers old man . No water metre . Lucky sod . Just one more thing then . What is your TDS going in and coming out .

[Smudger]

If it helps I had a Merlin a few years back - loved it - I put a pump on it ( same one as use now for 4040 ) - TDS in was 240 in 009 out and produced just under 100 litres an hour.

I only stopped using it because I inherited an RO4040 with a van and system I brought

Darran

[Steven Biggs]

Cheers smudger. That’s encouraging. Think I am leaning towards getting one . The annoying thing is , I have only moved 4 miles . But the water is a different source . I phoned Yorkshire water up today . In the 10 days I have been in the house the TDS has been 130 and everything up to 250 . And that is every day as well . This morning it was 250 . Just now 180 . One of there water technicians is phoning me back tomorrow. Try to explain it . It shouldn’t vary so much in one day , every day .

[AuRavelling79]

When it has new membranes - which work  out at about £200 for a set of two - I get about 4 - 6  coming out with 300/350 going in. But it soon (3 months) rises to about 10 - 12 and after a year is knocking around 12 - 16. When it creeps up past about 18 I get a pair of membranes. I'm on my third set in about 4 years.

You also have to replace the carbon filters which are about £20/£25 and last me about six weeks in the summer and eight weeks in the winter and then the flow slows a bit and I change it promptly as I believe a slow flow will speed up the deterioration of the membranes. (I did bulk buy a dozen somewhere on line at about £15)

It's not a the cheapest to run but if you have no meter it's acceptable. (To me anyway)

[Steven Biggs]

Thanks for the in depth reply . Makes it appealing if your not on a metre . But I am , so the water rejection rate would hurt . Gunna have to do some sums . If I stay double di , I reckon 2 sacks a month . If I get a merlin it may cost the same in water . Might have to look at another RO . More hassle .

[Smudger]

if you put a water meter in just in front of the RO system ( about 40 quid off Ebay ) you can get a different rate for all the water going through the RO system and you don't pay the sewage charge on this portion of water  - provided you don't put the waste water straight down the drain

Darran

[Steven Biggs]

After another 2 years of DI only , I finally got a Merlin on Friday . Got it set up , very happy with it . 300 in 17 out . The waste is about 2 to 1 . I am not that concerned as during the summer and any dry spells I will water the garden with it .  But I always thought my water pressure wad good . I open the tap and it gushes out , seems a really good flow . I have fitted the pressure gauge that came with the Merlin , and it shows 30 , even drops to 20 when the taps open in the kitchen and the shower is on . So I think I need a booster pump . Will this decrease the waste water or lower the TDS output ? Any recommendations for one , also a sub metre top put on maybe ? Don’t want to go above the recommended 38000 litres input . Cheers Barry .

[Spruce]

After another 2 years of DI only , I finally got a Merlin on Friday . Got it set up , very happy with it . 300 in 17 out . The waste is about 2 to 1 . I am not that concerned as during the summer and any dry spells I will water the garden with it .  But I always thought my water pressure wad good . I open the tap and it gushes out , seems a really good flow . I have fitted the pressure gauge that came with the Merlin , and it shows 30 , even drops to 20 when the taps open in the kitchen and the shower is on . So I think I need a booster pump . Will this decrease the waste water or lower the TDS output ? Any recommendations for one , also a sub metre top put on maybe ? Don’t want to go above the recommended 38000 litres input . Cheers Barry .

You could put a gate valve (or similar) on the waste line to restrict the water going to waste a little more.

[Steven Biggs]

Apart from decreasing the amount of waste water . Which is good . Would it use the membranes up faster .

[Steven Biggs]

Regarding the booster pump .I’m not interested in increasing the amount of water it produces . It does more than enough . Just wasn’t sure if it makes the membranes more efficient or less waste .

[Stoots]

I've always found 50/50 a more efficient cost ratio when on a meter.

[Smudger]

Mine was boosted and I got 009 from mid 300’s

I used a dab pump - others tend to buy Clarke pumps from machine mart

Darran

[Smudger]

I also put an extra carbon filter before the merlin as well

[Spruce]

Regarding the booster pump .I’m not interested in increasing the amount of water it produces . It does more than enough . Just wasn’t sure if it makes the membranes more efficient or less waste .

I have a 4040. Our water pressure is 50psi and when I last tested our delivery at the tap it was 13lpm of water. I have never run a booster pump but use an HF5 Axeon membrane. My r/o uses 4lpm of tap water.

I have my r/o set-up at about 55/45 waste/pure and that is the best ratio (sweet spot) for the system as it produces the lowest tds of pure from the r/o  before di.

If I open the waste more so have a ratio of around 2 waste to 1 pure my pressure gauges drop from 50 to 45psi and my rejection rate is similar. If I further open my waste tap to say 3 to 1 then the pressure on the membranes drops to around 40psi and my rejection rate  goes up.

Our tap water tds is 123 atm. I checked it this morning. The tds of the pure leaving the r/o is 3. If I use a ratio of around 3 to 1 then my tds goes up to 4 or 5ppm. These aren't big numbers, but they are big percentage wise. 

I've run my r/o like this for the last 8 years and that's how old my membrane is to the month this month. Yes, with time, membranes will wear out. (My rejection rate has dropped from 98% to 97% over the years.) But the biggest issue we all have is chlorine, as chlorine destroys the fabric material the membrane is made from. If your r/o is consuming more water than necessary, then your carbon block is going to have a shorter service life. This will have an effect on the membrane's longevity if it stops removing the chlorine from the water.

[Smudger]

Spruce - if you boosted that you would get down to 003

Darran

[Steven Biggs]

Thanks for all those replies . When you say the Merlin is not efficient with a low water pressure . What does that actually mean . Is it slow water production. Or is it using up the membranes faster , or does it mean the TDS is higher .

[Smudger]

TDS will be higher

Darran

[AuRavelling79]

I run my merlin off of tap pressure. I have a gauge but 'everyone' tells me I have very high pressure if it is accurate.

It varies between 55 and 70 psi. The higher the pressure gives a slightly better tds.

I suspect that I have prematurely damaged membranes in the past by not changing the carbon filter in good time. (38000 litres TOTAL)

So I bought a flow meter ready for the last change of membranes on 31st July. Put in a new carbon and sediment filter and changed both at 38000.

Membranes are at 9tds at the moment and I'm not bothering with resin at the moment. When it creeps above ten I will.

[Steven Biggs]

That’s great . Cleared that up for me . Thanks Darren , and old guy ,

[Steven Biggs]

Anyone recommend a booster pump for a Merlin . Will it make a difference 280 going in 16 coming out . But I assume that will go up in a bout 3 months . Just like Granville’s z

[AuRavelling79]

Anyone recommend a booster pump for a Merlin . Will it make a difference 280 going in 16 coming out . But I assume that will go up in a bout 3 months . Just like Granville’s z

What's the pressure?

[Spruce]

Spruce - if you boosted that you would get down to 003

Darran

Hi Darran, I'm already getting 3ppm without a booster. I can't see much of an improvement with boosted water pressure - 2ppm maybe. Hardly worth the extra effort and cost imho.

[AuRavelling79]

Spruce - if you boosted that you would get down to 003

Darran

Hi Darran, I'm already getting 3ppm without a booster. I can't see much of an improvement with boosted water pressure - 2ppm maybe. Hardly worth the extra effort and cost imho.

Just for clarity. You're talking 4040, yes?

[Spruce]

Spruce - if you boosted that you would get down to 003

Darran

Hi Darran, I'm already getting 3ppm without a booster. I can't see much of an improvement with boosted water pressure - 2ppm maybe. Hardly worth the extra effort and cost imho.

Just for clarity. You're talking 4040, yes?

Yes. The reason I started talking about my 4040 is that with the r/o running at its sweet spot the membrane has lasted well.  Steven Biggs was concerned that restricting the waste a little more would reduce the longevity of his PRF membranes. While I have no experience with a PRF r/o  I have to believe that making this mod won't have a detrimental result with regard to his membrane's longevity.

I also pointed out that having a higher waste to pure ratio means that his r/o is consuming more water. This means his carbon block's service life will be shorter even although he is producing the same amount of water.  I believe the carbon block is good for 38k of water. It doesn't take long to go through 38k of tap water.

I also agree with you that have a set of prefilters before the PRF makes good sense.

[Steven Biggs]

Anyone recommend a booster pump for a Merlin . Will it make a difference 280 going in 16 coming out . But I assume that will go up in a bout 3 months . Just like Granville’s z

What's the pressure?

pressure is only 30

[Smudger]

sorry - mis read the post

Darran

[Steven Biggs]

Where is the best , cheaoest place to get the carbon filters . I assume they are all the same , or do some suppliers sell inferior ones . Don’t want bro end up with rubbish . I would rather buy a few at a time .

[AuRavelling79]

Where is the best , cheaoest place to get the carbon filters . I assume they are all the same , or do some suppliers sell inferior ones . Don’t want bro end up with rubbish . I would rather buy a few at a time .

The carbon filters are unique to the Merlin/PRO I think.

I have looked around the net in the past and got ten at £15 plus vat each. But last time I found that £20 plus vat was the starting point with maybe a 5% discount for a £100 order.

[Steven Biggs]

Cheers old timer . Looks like that price is the going rate .