Watermaker -- Where Would You Put It?

[Fuss]

Originally Posted by rom

I just checked my logs, changed the 5u prefilter after 130h, was real dirty but only a light smell. I use my WM in the same way poiu does.
I guess the difference with your experience comes from where you use your WM ?

Could be. I will check more when I have time and report back if I have something to add.

On the subject of experience with 5 micron filters, they last 300 to 400 hrs and are cleaned with 4 bar water every 24-36 hours.
When they look well used and need cleaning after 12 hours we throw them out.

[poiu]

Originally Posted by Tellie

OK guys. Thanks Lodesman for posting the above instructions that came with this watermaker. The instructions are quite clear to me but I can certainly see how this can be confusing (pardon the snobbish sound). The instructions do not mean that fresh water itself will damage the membrane, what it is trying to say is that high pressure will certainly damage a membrane. What they are trying to prevent is a system that has it's needle valve set for pressures to begin the RO process in full on sea water. That's why they are telling you to open the valve all the way. Salinity of the water makes the difference in internal pressures and flow. The fresher the water the lower the pressures needs to be to produce product water. A standard plunger pump can easily exceed the 1000psi rating of a standard membrane. As the water gets fresher the other effect of a pre-set pump is the flow will increase. Membranes are designed for a set maximum flow as well, exceed this flow rating and pressure and you will certainly damage the membrane. Both of these effects would be the same with fresh water or salt. So this has nothing to do with it being fresh water. Also, water temperature can make a huge difference in the frequency needed for fresh water flushing. Run your watermaker in cold water and you could get away with longer flush intervals. But come further south, especially in the tropics, and the weekly flush may become an every three day flush or you will certainly be referred to my rule #2. One more way to look at it. I know many of you have or have had salt water flush heads. Remember what happens if after three days or so when you haven't used it? This is EXACTLY what happens inside a watermaker that has not been fresh water flushed. Again, ALL watermakers need to be fresh water flushed after each use and about once a week if not in use. If fresh water were a killer of membranes why would we use it with pickling agents? Every major watermaker company in the world adds a charcoal filter to their systems for fresh water flushing for very good reason. Why any company that wants to be in the watermaker business doesn't automatically add a fresh water flushing system or charges it as an extra add on to their units is almost reprehensible.

J.T. (aka Tellie)
HaldenMarineService@yahoo.com
(954) 515-7077
Spectra watermakers
BlueWater watermakers
RainMan watermakers

I suppose I could treat my membranes to a flush, I can only see it helping.

How do you do this - I have water in my fresh tank at 1.4 bar. Can I feed it using a 3 way diverter valve into the hose going to the HP pump. Then feed the water through a solenoid valve on a timer, a carbon filter and then a check valve to stop salt water getting in the fresh system (actually it shouldn't get in with a diverter valve and solenoid, but safer I guess)?

How much is needed to flush. My system has 3 RO filters. and I need about 35lt to pickle. If I don't flush the pre-filters I will need 10lt about less water to flush. Would maybe 15lt do the job?

I imagine you are only flushing the outside of the RO filters, so the flush will be done without the main pump, or is this wrong?

[Tellie]

Originally Posted by Jon Hacking

Tellie, thanks for this & for your earlier posts. It's apparent that you know your watermakers, & the rest of us on CF appreciate you sharing that knowledge.

What I'm hearing is that with direct drive CAT pumps, the pressures can go too high with fresh water, & that's the real reason some manufacturers are saying to reduce pressure when flushing. It's not that fresh water, per se, will damage the membrane, it's the higher pressures.

We've had a Spectra (380) for 16 years, & it seems to reduce the pressure on its own when we flush. That's how we know the fresh water has made it to the membrane - when the pressure goes down.

In fact, we'll sometimes take (fresh) deck water that's not quite drinkable & run that through the Spectra, to make it drinkable. There's nothing I can find in the manual about this, but it seems to work (& uses less power than processing salt water). Is this OK? TIA!

Yes it is OK, Spectras are self adjusting. It will only deliver the pressures and flow required according to the salinity or lack thereof. You can turn on your Spectra offshore and sail right into a fresh water lake with no problem and no adjusting needle valves. And it will fresh water flush after each use even in fresh water like a lake. We get a few destroyed membranes each year from those systems that won't compensate. But your Spectra is well ahead of the curve with this.

J.T. (aka Tellie)
HaldneMarineService@yahoo.com
(954) 515-7077
Spectra Watermakers
BlueWater watermakers
RainMan watermakers.

[carstenb]

I'll add my 2 cents. I've had a Spectra 200T running for almost 2 years - making about 150 liters every 3 days or so.

We flush 4 minutes after every usage - simple operation requiring turning 2 valves.

we've had zero, I repeat zero problems with the watermaker. I thought I had an issue with it, and when I was in Florida Tellie checked it out. We both thought the suction intake might be somewhat clogged.
I finally tracked down the problem - it was electrical >(not the watermaker) and I fixed it in about 15 minutes.

Is a watermaker expensive? well yes, depends - initial cost is high but if you demount it you can sell it used for about 2/3 what you paid for it - so the cost is actually only about 1/3.

The bonus is that you have almost unlimited fresh water and are entirely independent of land.

A watermaker is not an expense - it is a savings

[Quadrille in JB]

"Any way you can take a picture of that passage in your manual and post the pic here? There may be a bit of confusion. Fresh water can seriously damage a membrane if the pressures and flow are set for salt water and these are not compensated for as you move into fresh water. Temperature and salinity will affect pressures inside a system. I don't doubt what you are reading. I've seen some pretty strange advice over the years. But I can assure you, NOT fresh water flushing your system is a bad idea. Or they really like my rule number two above.

Tellie
I am on my second 'watermaker Jr.", a PUR Powersurvivor 35. The first one was in operation for over 10 years and it sold with boat. Now I've got an old used one, apparently with minimum hours on it, that works fine after a new membrane. I use this model due to space and power constraints on my 34' O'day. I've been very happy with both of them.
Question: I have never heard of flushing with fresh water before but it sounds like a good idea. We usually have to let our system run for about 10 minutes after start up before we start getting good water. Will it be okay to simply install a 3-way valve plumbed into the boats fresh water system for flushing. Do I have to worry about pressure differences as you stated in the above quote? Thanks for all of your advice.

[boom23]

Originally Posted by rom

I am no expert and I am following the manual, Dessalator here. What they say is that fresh water is number 1 enemy of membranes. So if you fresh water flush, then you have to flush again with salt water before putting pressure the next time you use it. It is a BIG warning in the manual. Does it make sense to you ?

Also, their advice is to rinse the membranes once a week, and "doing it after every use would be a waste of fresh water".

I read the Dessalator comment about the fresh water flush also. I believe they might be referring to the potential chlorine (from land based fresh water)? Chlorine is bad for membranes.

I am not sure if the Dessalator has a carbon filter (to remove chlorine) for the fresh water flush. Maybe you can replace the 5 micron filter with a carbon before the flush?

The Spectra watermakers do, and recommend, fresh water flush through a carbon filter.