Which pre-filters do I need?

[Kenzor]

Tried searching online for filters that fit this system but not sure which ones I need? Someone recommended I buy the ones from eBay in the photo but now I’m being told these won’t fit my system? What do I do?

 

[spruce]

Tried searching online for filters that fit this system but not sure which ones I need? Someone recommended I buy the ones from eBay in the photo but now I’m being told these won’t fit my system? What do I do?

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This looks like a PRF-RO. It started life as a Merlin.

This means that the filters you pictured are incorrect.

A PRF-RO has a combined Fiberdyne/sediment filter and 2 r/o membranes.

Here is the prefilter x 1

https://www.gapswater.co.uk/acatalog/PRF-RO---GE-Merlin-Replacement-Carbon-Fibredyne-Pre-Filter--PN-303833-3038333.html#SID=458

The membranes only need changing when they stop working efficiently - x 2.

https://www.gapswater.co.uk/acatalog/PRF-RO---GE-Merlin-Replacement-RO-Membrane--TLC-350--PN-4000569-4000569.html#SID=458

Instruction manual

https://www.gapswater.co.uk/acatalog/prfromanual.pdf

A fellow window cleaner has a Merlin. He has fitted an inline prefilter before the r/o as our water can be laden with sediment at times. He uses a standard 10" prefilter with 1/2" bsp fittings.

This is an example

https://www.gapswater.co.uk/acatalog/Pentair-Pentek-10--3G-Slimline-Housing-with-Integral-Bracket--1-2--Ports--with-Pressure-Release-158628.html#SID=551

Sediment filter

https://www.gapswater.co.uk/acatalog/SPECTRUM-Economic-Spun-Bonded-TruDepth-Filter--ESP_5.html#SID=844

Tick box for 9 7/8" size

 

[Kenzor]

@spruce Thanks for all the info, it’s really helpful!

I’m thinking maybe I should get a new prefilter to begin with and see how it goes from there since those membranes seem pretty expensive, don’t know if there’s cheaper options? I don’t want to scrimp on paying for my kit but I guess that’s the cost of business. Can you recommend a decent resin as well?

 

[spruce]

@spruce Thanks for all the info, it’s really helpful!

I’m thinking maybe I should get a new prefilter to begin with and see how it goes from there since those membranes seem pretty expensive, don’t know if there’s cheaper options? I don’t want to scrimp on paying for my kit but I guess that’s the cost of business. Can you recommend a decent resin as well?

For me its Tulsion MB115 available from Daqua or Gardiners.

The main prefilter you will replace regularily is the sediment/Fiberdyne prefilter. (The service life of a Pentair Fiberdyne prefilter is 38000 liters. This includes waste as well as pure.) Its important to replace this prefilter according to the manufacturers guidelines as this prefilter removes chlorine from the water. Chlorine destroys the material membranes are made from.) Before I purchase a prefilter I would work out if the membranes need replacing first.

You need to work out how efficiently your r/o is working to decide whether you need to replace membranes as well.

This r/o isn't really manufactured with window cleaning in mind. Its designed as an undercounter addition in American kitchens; a third tap, and as such doesn't need to be really efficient at removing all the total dissolved solids in the drinking water it produces.

On the other hand we need the most efficient membranes as the less efficient they are the more resin we are going to use to remove those solids from the water we clean windows with.

If memory serves me the supplier's information is that if the r/o is removing 95 to 90% of the dissolved solids in your water its operating to spec. So if your water is 300ppm at the tap then your pure will read between 15ppm and 30ppm. But at 30ppm you are going to be using a lot of resin. If you test your product water and find that your r/o is not achieving the efficiency the manufacturers suggest, ie lower than 90%, then you should consider replacing membranes. (Having a high water pressure does help these r/o run more efficiently.)

If you need to replace membranes then my suggestion is to throw it away and get a more efficient r/o such as a 4021. A point to consider though is that the only (in my opinion) advantage with a PRF is that a ball valve in the tank switches the whole r/o off when the tank is full. Changing over to a 4021 will mean an additional float switch and solenoid valve. But using the above example, a 4021 or a larger 4040 should be around 97% efficient. This means the product water from the r/o will be around 9ppm or less, thus reducing your monthly resin costs.

My r/o is a 4040 with an HF5 membrane. When I first fitted the membrane nearly 7 years ago it was removing 98% of the tds in our water. Its now down to 97%.

It helps that out tap water tds is less than 150ppm, but the 20" Fiberdyne prefilter gets religiously changed when its 76,000 liters service life has expired.