Letting WM membrane sit with salt water for 24h

[LifesBetterWhenYoureBeating]

When I'm by myself on the boat I need to run the watermaker for around 1h a week to supply my needs, but the recommendation is to not let it sit for more than 5 days so what I usually do is run the WM for 20 minutes or so for 3 consecutive days, with no fresh water flush in between. Then I do a fresh water flush, clean the pre filters and let them dry before putting them back in.

This way I clean the pre-filters once every 8 days instead of once every 5 days, but I wonder if leaving the membrane sit for 24h with salt water can reduce its lifetime?

Thanks in advance!

Sent from my SM-A225F using Cruisers Sailing Forum mobile app

[sailorboy1]

Every time I have seen a similar question the answer is you probably don't need to fresh water flush the WM if you are going to run it again the next day. But if not it really should be fresh water flushed.

I got fresh water "cheap" a few months ago and didn't flush enough, or waited too long between. Now my system that was making 35 gph is dong 22-25 gph because of membrane fouling. That is going to be $500 to fix when I get back somewhere I can.

So now I am fresh flushing 1.5 minutes after each use (about 5 gal) instead of just 1 minute. And I either make water or reflush every 5 days.

If I only had to run my WM an hour a week I definitely would run the extra 20 minutes and do a real good flush after and I would do this every 5 days regardless. Is running the WM enough of a "problem" that you would prefer to have to replace membranes etc. instead???

[Lepke]

Fouled membranes can be cleaned. Plugged membranes can be cleaned by back flushing. It's not rocket science.

[Pitchondesign]

I run my wm every day, without any flush or fresh water rinse. My last membrane lasted 10 years. The only reason I changed it was because it was 10 years old. All pressures and flow rate were within spec, and PPM was below 200. Admittedly, this was in the Bahamas. Other areas would be different.

[SailingHarmonie]

Originally Posted by Lepke

Fouled membranes can be cleaned. Plugged membranes can be cleaned by back flushing. It's not rocket science.

What exactly do you mean by “backflushing”? Membrane makers typically do not recommend any back pressure at all….

[sailorboy1]

Originally Posted by Lepke

Fouled membranes can be cleaned. Plugged membranes can be cleaned by back flushing. It's not rocket science.

have you successfully done it?

Didn't work for me

[newhaul]

Originally Posted by sailorboy1

have you successfully done it?

Didn't work for me

That's what I like about my powersurvivor35 it came with a membrane cleaning pressure vessel that allows for free flow of cleaning solutions .
But they all can be cleaned using the pickling setup and the cleaning solution for scale removal
https://www.boundlessoutfitters.com/...over-1-lb-jar/
They also make one to clean the organic matter out as well .
https://www.boundlessoutfitters.com/...anic-5-lb-tub/

[Lepke]

Originally Posted by sailorboy1

have you successfully done it?

Didn't work for me

Backflushing
I live aboard and I make water in fresh and salt. There are several filters before the membranes down to 1 micron. My home dock is on the Columbia River and it can be silty. I forgot to check my filters and plugged the membranes with river silt.
To backflush, I use a Y so water enters the opposite end of the membranes at the same pressure so I don't have a excessive pressure drop. I start with the pressure all the way down and gradually increase to to about 100psi. I let it run for an hour and the membranes make water like before. Tds on fresh is about 5 and below 150 on salt. Membranes are going on 11 years. And I have the water tested about once a year.
Sometimes when the system sits too long in fresh w/o use I get marine growth. I flush with sodium hydroxide to clean, usually yearly. I've never pickled them.

[newhaul]

Originally Posted by Lepke

Backflushing
I live aboard and I make water in fresh and salt. There are several filters before the membranes down to 1 micron. My home dock is on the Columbia River and it can be silty. I forgot to check my filters and plugged the membranes with river silt.
To backflush, I use a Y so water enters the opposite end of the membranes at the same pressure so I don't have a excessive pressure drop. I start with the pressure all the way down and gradually increase to to about 100psi. I let it run for an hour and the membranes make water like before. Tds on fresh is about 5 and below 150 on salt. Membranes are going on 11 years. And I have the water tested about once a year.
Sometimes when the system sits too long in fresh w/o use I get marine growth. I flush with sodium hydroxide to clean, usually yearly. I've never pickled them.

I pickle mine every winter when cruising my home waters puget sound use rv potable water antifreeze propylene glycol. Just follow your manufacturer instructions for pickling

[sailingharry]

A word of caution on RV antifreeze. It all looks the same, but some is PG, some is ethanol (alcohol), and some is a mixture. Most is poorly labeled -- although price is often the best indicator. Ethanol will kill plastic components (pumps, filter bowls, etc) on boat systems and I assume it is even worse for water makers.

Read labels carefully!

[newhaul]

Originally Posted by sailingharry

A word of caution on RV antifreeze. It all looks the same, but some is PG, some is ethanol (alcohol), and some is a mixture. Most is poorly labeled -- although price is often the best indicator. Ethanol will kill plastic components (pumps, filter bowls, etc) on boat systems and I assume it is even worse for water makers.

Read labels carefully!

Hence I specified Propylene Glycol .

[sailingharry]

Originally Posted by newhaul

Hence I specified Propylene Glycol .

That was not specifically directed at you. I suspect that you were using the right thing, as you said the right words. It was more of a generalized PSA. I know in my early days, when winterizing my boat, I made that mistake.

[Pizzazz]

You are worrying too much about this from an outdated perspective that you should baby the membrane. The typical SW membrane (2540) costs $200. Most of us change engine oil annually, why would you want to keep your membrane for 10 years? My experience is as follows:

- Survivor 35 membrane from eBay. Was maintained annually with glycol until 2006, then sat in storage for 12 years. Dry. Got it, worked liked a champ, the watermaker was run once a month with no cleaning and lasted until I sold the boat (3+ years).

- Another 2514 membrane, ran monthly with no fresh water flush, gradually started reducing output which was restored just by doing a fresh water flush.

- Another 2540 membrane, dead on arrival, replaced by the manufacturer.

I suggest use the water maker as you need it, try to run it for a few minutes at the end with no pressure (i.e. salt water flush) and if you see the output decreasing by more than 20-30%, only then do a fresh water flush. If you clog it, don't bother with cleaning chemicals (they are half the cost of a new membrane), just replace the thing.

[newhaul]

Originally Posted by Pizzazz

You are worrying too much about this from an outdated perspective that you should baby the membrane. The typical SW membrane (2540) costs $200. Most of us change engine oil annually, why would you want to keep your membrane for 10 years? My experience is as follows:

- Survivor 35 membrane from eBay. Was maintained annually with glycol until 2006, then sat in storage for 12 years. Dry. Got it, worked liked a champ, the watermaker was run once a month with no cleaning and lasted until I sold the boat (3+ years).

- Another 2514 membrane, ran monthly with no fresh water flush, gradually started reducing output which was restored just by doing a fresh water flush.

- Another 2540 membrane, dead on arrival, replaced by the manufacturer.

I suggest use the water maker as you need it, try to run it for a few minutes at the end with no pressure (i.e. salt water flush) and if you see the output decreasing by more than 20-30%, only then do a fresh water flush. If you clog it, don't bother with cleaning chemicals (they are half the cost of a new membrane), just replace the thing.

Well mine costs $400 so worth the occasional cleaning when ppm goes over 350.
Cost me $20 for a bottle that has enough powder to do a dozen cleanings .

[Lepke]

Originally Posted by newhaul

Well mine costs $400 so worth the occasional cleaning when ppm goes over 350.
Cost me $20 for a bottle that has enough powder to do a dozen cleanings .

Yep, the cleaning chemical is cheap. Why change membranes that are working within spec's?