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Old 10-04-2010, 04:02   #16
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You have to use them..fresh water flushing doesn't keep them clean....if you don't use it, put biocide in it and leave it standing...be careful when restarting not to put biocide in your tanks...mine has a depressurisation valve that allows rinsing without water production
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Old 10-04-2010, 06:36   #17
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Since a small unit like the PUR 40 will produce 1.5 gph, or 36 per day, how could you use that much water on a small boat with 2-4 people ? Unless your wasting it...
You want to run your watermaker 24/7?
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Old 10-04-2010, 10:07   #18
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You want to run your watermaker 24/7?
A ha, now there is a question, 14 US gallons a day is 50 litres. I know we (2 of us) use about 25 litres per day (LPD) cruising NW Europe, but that is with showers ashore, so it could be 50 - 75 LPD given how long SWMBO spends in the shower. So that would require 10-15 hours a day which does sound quite a long time to run the little PUR 40. Decisions, decisions.

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Old 10-04-2010, 14:54   #19
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Hi Pete, my pur 40E, I ran it when I was inspecting the yacht, bought the yacht, then had to rush back to the airport to get home for Christmas and did not biocide the water maker, nor flush it with clean water, just did not know how to do it!

When I returned in 3 weeks to Langkawi, the whole system was black, stank rotten and so I cleaned it, threw away the filter and biocided it.

Still haven't dared to use it now for 4 months, finally got some biocide in Australia, it is waiting for me in Langkawi.
I know a lot of people who just carry them around and wont use them!
When it worked it produced the promised 4 litres per hour of sweet water.
Keith.
what are you telling us? not sure why you would post the above are you just confirming that if you ignore the instructions and do the opposite it will fail?
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Old 10-04-2010, 15:25   #20
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small watermakers give you much more trouble than big ones. Remember that a membrane is a self-cleaning cross-flow filter and it needs a lot of cross-flow to keep it clean. take a look at a big one and calculate how long you have to run it with 2 days to a week in between. This will narrow you down to possible choices because you should favor the biggest one you can run or buy within that range of possibilities.

Example: if you need 25 liters a day (say 7 gallons) and want to run it once a week (that is the minimum frequency to target). You need 7 x 7 = 49 gallons. With two big membranes that brings you to just over 1 hour run time weekly or with one big membrane to 2.5 hours weekly. I would put the high end of the possibilities at 1 big membrane 20gph in that case. So, if I could afford that and have the power for running it, you're done. All the rest is a compromise imo.
While you do these calculations, take a step back and think about:
- fresh water flush toilets (best thing we bought)
- fresh water deck wash (saved 90% time on polishing stainless)
- washing machine?

and do the math again.

cheers,
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Old 10-04-2010, 15:31   #21
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Nick, once again thanks

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Old 10-04-2010, 18:38   #22
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We have a Pur Survivor 160 which produces abot 6.5 gph. Backflushing etc is a bit of a pain as is the low output. We have a water intensive boat with Fresh water flush toilets, a washing machine, etc. We don't use the washing machine much but we find we go through out 120 gallons in 5-6 days with 2-3 people on board. This means we need to run the water maker every couple of days to keep up and keep the membrane clean. Since it draws about 20 amps at 12 volts we tend to run it when we are generating power with the engine or genset. My 300 watt solar panels don't keep up with my electrical consumption without running the motors every couple of days in the winter time. The problem is that it takes about 10 hours of generator or engine time to make half a tank of water. The watermaker was in the boat when I bought it. If I was doing this from scratch I would try to get a 30 GPH 120v watermaker so I could get by with a couple of hours of genset time while topping the batteries every couple of days.
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Old 10-04-2010, 19:36   #23
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We have a Pur Survivor 160 which produces abot 6.5 gph. Backflushing etc is a bit of a pain as is the low output. We have a water intensive boat with Fresh water flush toilets, a washing machine, etc. We don't use the washing machine much but we find we go through out 120 gallons in 5-6 days with 2-3 people on board. This means we need to run the water maker every couple of days to keep up and keep the membrane clean. Since it draws about 20 amps at 12 volts we tend to run it when we are generating power with the engine or genset. My 300 watt solar panels don't keep up with my electrical consumption without running the motors every couple of days in the winter time. The problem is that it takes about 10 hours of generator or engine time to make half a tank of water. The watermaker was in the boat when I bought it. If I was doing this from scratch I would try to get a 30 GPH 120v watermaker so I could get by with a couple of hours of genset time while topping the batteries every couple of days.
Or bite the bullet and buy a Spectra.
I recently sent in our 180's Clark Pump to be updated by the factory.
When I got it back, it did indeed perform 15% better than before.
Now I get slightly over 200 gpd at 12.8 volts (solar keeping up) @ 8 amps.
No genset on our boat, and I HATE running the engine.
We almost never have more than 2 people aboard and no washing machine, but fresh water flush is looking attractive.
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Old 10-04-2010, 20:01   #24
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Small watermakers give you much more trouble than big ones. Remember that a membrane is a self-cleaning cross-flow filter and it needs a lot of cross-flow to keep it clean.
This claim could use a supporting reference. I don't follow your reasoning.
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Old 10-04-2010, 21:52   #25
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Here you have the options: a Clark pump (I believe it's not just Spectra selling that) on 12V DC or a big AC powered one. The 3rd option that some go for is an engine mounted system but I would stay away from that.

The Clark pump is 3 times as efficient than the average AC powered watermaker. However, at 8gph output, you have to run it long plus more to make the water for flushing it. If you have a genset the choice is easy: big AC powered so that you only need as little run time on the genset as possible, like 1 to 3 hours per week. If you have no genset you go the DC path with a Clark pump and I know from looking around me that it'll give more trouble than the big units... but there's no genset to worry about.

ciao!
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Old 10-04-2010, 21:55   #26
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This claim could use a supporting reference. I don't follow your reasoning.
Research how membranes work and you'll see. The less cross flow (which is "reject" or "brine reject") the less cleaning, the more trouble. That's how membranes are. It's also the reason the 2nd membrane (when two are connected in series) fails first... it has less cross flow.

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Old 10-04-2010, 22:02   #27
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Nick - Okay, I understand your reasoning now. Yes, the small efficient Spectra-like systems are rather techy and probably more failure prone. Very happy with mine though. Totally automatic. No chemicals. A few sensor glitches at first, but all good for 3 years now. Just push the START button. Solar powered.
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Old 11-04-2010, 00:10   #28
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Yes, but at three years, you're just passing the break-in period for the membrane(s). Our's are 7 years old now and still well within specs (300 ppm).
So, while the techyness is one part of it, the question is how long the membranes will last.

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Old 11-04-2010, 01:05   #29
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Hi Meyermm, yep, there were no instructions, there was a switch marked, watermaker, I just switched it on and it made water! I bought the boat without the seller, he was a continent away, just flew there and bought it. Anyway, there wasn't any biocide and I thought it would be ok for 3 weeks. But it wasn't, apparently there is no real harm done.
So the post was to let people know that the watermakers are not just a machine to produce potable water from seawater or whatever, they are a complex device that needs a fair amount of knowledge and chemicals to keep running properly, well mine is!
Keith.
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Old 11-04-2010, 01:57   #30
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So the post was to let people know that the watermakers are not just a machine to produce potable water from seawater or whatever, they are a complex device that needs a fair amount of knowledge and chemicals to keep running properly, well mine is!
Keith.
They are really quite simple and in 3 1/2 years or running ours (Large AC unit) The only chemicals I consumed was some metabisulpahte, available from Home Brew and wine making supplys, when we pickled it whilst away from the boat for more than a month or two and the only maintenace was a new capacitor on electric motor, production was just as good as day we started, I built unit myself, its not rocket science and components are cheaper than ever, we used a brass triplex pump (Hawk model) and it never missed a beat and at price about a third cheaper than fancy stainless titanium ones. to my mind the commercially made watermakers are over complicated to justify the amount they charge.
I have never met any one with one of the small Pur Survivor models who has been happy. go as big as you can you'll never regret it!!
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