Jump to content







Before posting a new topic please use the search feature. Duplicate posts may be removed or merged with others.

Start new topic


Lufc

Pentair merlin waste water

Recommended Posts

Lufc

Anyone got one . I had the old Merlin about 10 years ago . And was happy with it . But I decided to go double di as my tap TDS was about 70 . But the tap TDS is now 200 . So I  am gunna have to get some kind of ro . I can’t be bothered with static tanks , transfer pumps and flushing etc . I like the thought of turning it on and filling the van . A bit like di , but with waste water . Which is my only concern. So are the new Merlins more efficient regarding the pure to waste water ratio ? Cheers Elliot . 

Share this post


Link to post
spruce
Posted (edited)
10 hours ago, Lufc said:

Anyone got one . I had the old Merlin about 10 years ago . And was happy with it . But I decided to go double di as my tap TDS was about 70 . But the tap TDS is now 200 . So I  am gunna have to get some kind of ro . I can’t be bothered with static tanks , transfer pumps and flushing etc . I like the thought of turning it on and filling the van . A bit like di , but with waste water . Which is my only concern. So are the new Merlins more efficient regarding the pure to waste water ratio ? Cheers Elliot . 

 

Apparently, but not much and still not quite as efficient as a similar size 4021. Alex Gardiner had a spec sheet on his website when he sold this r/o and it says it has a 3 to 1 waste to pure. The old Merlins were 5 to 1.

 

My mate down the road has an old Merlin and from new its only removed around 90% of the dissolved solids in the water. My 4040 is removing 97% and that's 7 years old in September from the same water source. My mate uses a lot more resin than I do as well.

He also fitted an additional inline sediment filter to save his carbon block and later fitted a gate valve onto his waste line so he could throttle back and reduce the amount of water going to waste.

 

A moderator on the other window cleaning forum bought a PRF-RO off Gardiners a number of years ago. He has good (much higher than average) water pressure in Bristol and he gets around 94% rejection rate if memory serves me. Alex mentioned that this is within the spec of this r/o and is slightly better than their specs on their website before they discontinued selling it along with other water filtration lines.

Edited by spruce

Share this post


Link to post
Lufc

Cheers for that spruce . So I could be looking at 3 litres down the drain for every litre of pure . Ouch . Are there any other alternatives . 

Share this post


Link to post
spruce
Posted (edited)
3 hours ago, Lufc said:

Cheers for that spruce . So I could be looking at 3 litres down the drain for every litre of pure . Ouch . Are there any other alternatives . 

 

4040 or a 4021. A 4021 is half the size of a 4040 and will produce about the same amount of water a PRF-RO will do. The only downside is that it isn't half the price of a 4040. If you should ever upgrade you can add a second r/o housing and membrane, but further down the line you will have to replace 2 membranes rather than a single 4040 membrane. 2 x 4021 membranes cost more than 1 x 4040 membrane. I would spend a little more money and go for a 4040 with an Axeon HF5 membrane. (HF5 membranes are also available for 4021 r/o's.)

There are much cheaper Chinese manufactured membranes on the market boasting rejection rates better than an American made Axeon membrane. Do not be taken in by their false advertising.

If you want to talk to a genuine supplier then speak to @doug atkinson at Daqua.co.uk and he will help you.

 

The Merlin had a good feature in that when you switch the pure flow off a valve shut the flow of water into the r/o as well. It was easy to fit a ball float valve in your storage tank and when the tank was full the r/o would stop producing water.

But for the amount I save on water and resin compared to my mate down the road, fitting a float switch and solenoid valve will soon pay for itself.

 

Our tds is around the 130ppm atm. My r/o waste gate is set at about 55 waste to 45 pure. My product water is 3ppm from the r/o before di. My mate's r/o down the road is 13ppm. The only reason he is using less water is because he has a gate valve on his waste to reduce his waste to the drain.

 

Edited by spruce

Share this post


Link to post
Lufc

Cheers spruce . As usual very informative. Just got to workout my water bill . 3000 litres of pure . Might mean 9000 down the drain . Total 12000 litres of water every week . Might be in the region of £40 a week . 

Share this post


Link to post
spruce
Posted (edited)
10 hours ago, Lufc said:

Cheers spruce . As usual very informative. Just got to workout my water bill . 3000 litres of pure . Might mean 9000 down the drain . Total 12000 litres of water every week . Might be in the region of £40 a week . 

 

This is where due dilligence comes in - counting the cost before making a purchase decision.

Remember to add the additional sewage charge to your water bill costs as well.

 

On a water meter those more expensive r/o's will pay for themselves in no time.

Add the extra cost of resin and your saving will quickly mount up.

 

The same is true with a cheap chinese manufactured membrane. You might save £100 to begin with but the extra cost of resin polishing off the product water will soon negate that saving and cost you more over the long run.

 

Some water authorities will allow you to claim back a sewage charge on the pure you take away. If you send the waste to a soak away then they might refund that sewage element as well. But in practical terms, sending 9000 litres to a soak away is a tall ask imho. Our water authority will not entertain a refund on the sewerage element period, so those on a meter have to include the r/o water and the sewerage element as a business expense. The way to do this is to add a seperate water meter to your r/o inlet.

 

Look at @Damo's advice on this thread. His explanation should be made a sticky imho. @Gav

https://windowcleaningforums.co.uk/topic/28404-water-billing-question/?tab=comments#comment-404800

 

Edited by spruce

Share this post


Link to post

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

×
×
  • Create New...

Important Information

We have placed cookies on your device to help make this website better. You can adjust your cookie settings, otherwise we'll assume you're okay to continue.