[berwick1]

I have been helping a friend with a watermaker issue and we are stumped. His flow rate went way down and his PPM went way up. The watermaker manufacturer told him his membrane was shot, sounds reasonable, had another one shipped to Georgetown, Exumas. The new membrane had the same issue, we can get the pressure up to 800 PSI (with the valve is fully closed) where my WM seems to have lots in reserve, but the output is down to about 6 gph vice the 20 gph it should be and PPM stil way too high. The manufacture is saying it must still be the membrane, shipped another in, the same issue!!! Thought maybe it is a pump issue, took apart the valves and they seem to be working as one way valves when blowing through them. Didn't go any further with the pump and don't have another to swap with.
Any ideas? Could the pump not be working right even though we can get the pressure up to 800 PSI (barely though). It had too much oil in it, could that have gotten into the system and mess a membrane up very quickly, yet cause the output to be low?

thanks
Richard

 

[Minnewaska]

You should identify the make and model, so that someone familiar with it might help you.

This "technical forum" is supposed to be about technical issues with this website. Your thread belongs in Gear and Maintenance. I suppose you could delete your post and start over, but not a life and death problem.

 

[berwick1]

How do I delete it?

Richard

 

[hellosailor]

Pressure is high but dissolved solids are also high.

That could mean the dissolved solids from the *waste* stream are somehow getting back into the pure water output. A valve or plumbing failure perhaps?

 

[Omatako]

800psi is about right. What sort of TSD levels are you getting? Anything below 200 is potable and at that pressure you should get that from a good (new) membrane.

Oil in the membrane is a death sentence for the membrane - AFAIK almost immediately. If you think you have pumped oil into the new membrane that could be the problem. And unless I'm mistaken (often am) oil will also reduce yield dramatically at the same time as producing high TSDs

 

[Skipper Jer]

Could one place the suspected membrane in fresh water to look for an oil slick?

 

[Delezynski]

Richard,

Has he carefully CAREFULLY inspected the end caps (and any end fittings) for cracks AND replaced the "O" rings? Sounds like a small leak from the HP side to the product side.

Greg

 

[RichH]

Did you folks follow the specific 'start-up' procedures for the FilmTek polysulphone membranes? ( FilmTek membranes are the 'most common' (~98%) cartridges used in recreational watermakers).

Did you specifically apply a waterproof silicone based grease to the O-rings? .... prevents rolling and 'twisting/pinching' of the O rings during cartridge installation ..... and if omitted can easily cause leakage from the input (retentate) side to the output (permeate) side .... such leakage will show up as a TDS value greater than 200 ppm after (slow) 'start up'.
NEW O-rings should be used each time when changing RO cartridges, even if you remove a new cartridge and immediately re-install.

Here's an access link to the FilmTek 'tech manual', which includes methodolgy for installation, membrane 'start-up' .....
{It also includes CLEANING and regeneration procedures, etc. ... but recommended ONLY if you have the 'chemical expertise' to do so, as some of the chemicals used are quite hazardous/dangerous}.

If you dont follow the 'start-up' procedures precisely, its easy to break, etc. a new membrane. Even that the membrane is 'water wettable - hydrophillic', it can if not 'started' correctly can become 'air bound' which 'can' partly block the flow to the 'permeate'/product side ... the precise startup procedures, including slowly 'ramping-up in flow rate and pressure', take this into account. One must fully 'purge' all air from the cartridge before full operation.
Tech Manual - http://www.chesterpaul.com/pdf/filmtec/FILMTEC Technical Manual.pdf

Also, from your description, be sure to check the pressure drop/flow across those 'prefilters' as if youre not getting designed minimum flow to the hi-pressure pump you can stall the pump and ruin it if it overheats due to lack of input flow .... check the 'feed' pump and its 'strainer' for flow rate while youre at it.

FWIW .... I wouldnt use a watermaker anywhere near the Georgetown harbor ... or any other harbor with a high concentration of boats (dumping sewage). Also, if there is a 'bloom' of any microscopic sea life going on ... will/can quickly extrude through the prefilters and quickly foul a RO membrane --- look for 'cloudiness' in the water. Dip a clean glass into the harbor etc., hold it up to strong sunlight and if you denote a significant 'haze' in the water .... dont use the watermaker.

;-)