Visit our Popular Forums

Cheechako · 16-10-2021, 10:54

Well, that's tough to get done. OTOH, a membrane is just not that expensive in the scheme of things. If the unit seems to work fine mechanically in the river, you have low risk.
Even if you test do you have the ability to know how well it's working? Just a taste test? Be sure all the storage chemicals are out if you taste test!

I have bought boats which were sea trialed in salt water. They had watermakers but I didn't test them. Why? The problem is, as a potential buyer, you are responsible to restore the watermaker to "storage condition" if you operate it. Just like you pay for launching and pressure washing or whatever else you need to do to inspect it. Are you prepared to do that?

Lepke · 16-10-2021, 11:18

All winter, I make water in fresh water. It doesn't hurt the membranes. And when making water in salt water, I make an extra 5 gallons and flush the system at the end, leaving it sitting in fresh.
When you make water in fresh, you turn the pressure way down, and you get very low tds. Good enough for batteries.
In a river, you need more prefilters, especially if it's silty or you can plug the membrane. Fixable with a reverse flush.

**Tellie** · 16-10-2021, 11:35

Quote:

Originally Posted by gsalgado

Thanks @Tellie, I'm definitely going to test it as best as I can before buying, but the survey/trial is in just 3 days and I don't think I'll be able to get a hydrometer (either in Rio Dulce or online) in time. However, maybe I could feed it salty mineral (to ensure it's not chlorinated) water ? If I go down that route, would it be enough to use a TDS meter (which I'm hoping someone in the area may be able to lend me) before/after adding salt to the water, to ensure it's salty enough? Also, how much water do you think I'd need for that?

OK, I know it's tough sometimes to get to offshore water. But as Cheechako mentioned, membranes are relatively inexpensive. There is no way to test if the membrane is any good unless you know the salinity or lack of coming into the watermaker. Even a totally bad membrane will look good in fresh water. But I would still run the system regardless and run it through all it's paces through the control panel. This will tell you the condition of the sensors, the condition of the feed pump, Clark pump symmetry, coils, salinity probe, etc. Before you head out there to the boat take a look at the manual and go through how to operate the system and familiarize yourself a bit with the operating procedures and how the control panel functions and it's alarms. A standard TDS meter is useless here. It can read the output water but the input water would be too high in salinity for it to read. Good TDS meters that can read the input are expensive and not worth the investment for your situation. Without an accurate input TDS reading any out put readings are meaningless. If you have any questions just ask.

http://marinewarehouse.net/images/Sp...II_mpc5000.pdf

Cheechako · 16-10-2021, 11:44

Quote:

Originally Posted by Lepke

All winter, I make water in fresh water. It doesn't hurt the membranes. And when making water in salt water, I make an extra 5 gallons and flush the system at the end, leaving it sitting in fresh.
When you make water in fresh, you turn the pressure way down, and you get very low tds. Good enough for batteries.
In a river, you need more prefilters, especially if it's silty or you can plug the membrane. Fixable with a reverse flush.

Yeah. But I think his problem will be telling if the RO unit makes good water from salt water.

GreenWave · 16-10-2021, 17:11

Quote:

Originally Posted by Cheechako

Well, that's tough to get done. OTOH, a membrane is just not that expensive in the scheme of things. If the unit seems to work fine mechanically in the river, you have low risk.
Even if you test do you have the ability to know how well it's working? Just a taste test? Be sure all the storage chemicals are out if you taste test!

I have bought boats which were sea trialed in salt water. They had watermakers but I didn't test them. Why? The problem is, as a potential buyer, you are responsible to restore the watermaker to "storage condition" if you operate it. Just like you pay for launching and pressure washing or whatever else you need to do to inspect it. Are you prepared to do that?

Exactly!

LifesBetterWhenYoureBeating · 16-10-2021, 17:33

Quote:

Originally Posted by Cheechako

...

I have bought boats which were sea trialed in salt water. They had watermakers but I didn't test them. Why? The problem is, as a potential buyer, you are responsible to restore the watermaker to "storage condition" if you operate it. Just like you pay for launching and pressure washing or whatever else you need to do to inspect it. Are you prepared to do that?

I'm already paying for a rigging inspection and a survey... I'd rather pay a bit extra and have the WM properly checked than running the risk of wasting time/money later to repair it

waterman46 · 16-10-2021, 17:44

Quote:

Originally Posted by gsalgado

Hi there,

I'm in the process of buying a sailboat which is in a river (Rio Dulce) and that's where the "sea" trial will take place, so I'm wondering how I could go about testing that the watermaker is actually able to desalinate water... Would it be possible to use a bucket of salty water to feed it? Any other suggestions?

Cheers

Mix some artificial sea water: 35g salt per liter of fresh non-chlorinated water. The TDS meter probably would not measure that much salt - it would be off the scale but the exact concentration is not really important. TDS of watermaker output should be less than 250 ppm. Our old Spectra usually got down around 120ppm or so. The TDS may start out high and reduce as system runs. Usually it takes about 5 minutes of runtime for the product water salt content to stabilize.

Fore and Aft · 16-10-2021, 17:57

I have surveyed countless boats with water makers and would probably ever only seen a handful working. Like Cheechako says you have to return it to the state you found it in. That can be a real issue if the owner is not around or the owner is unhappy for anyone else to do the job.
Most buyers I know are happy to take the owners word for it and are happy just to see the panel light up and maybe hear the pump motor kick in. That might not be perfect but you have to realise it is not a new unit and there is a possibility even after the testing next time you use it might not work anyway.

Cheers

**Tellie** · 16-10-2021, 18:21

Quote:

Originally Posted by Fore and Aft

I have surveyed countless boats with water makers and would probably ever only seen a handful working. Like Cheechako says you have to return it to the state you found it in. That can be a real issue if the owner is not around or the owner is unhappy for anyone else to do the job.
Most buyers I know are happy to take the owners word for it and are happy just to see the panel light up and maybe hear the pump motor kick in. That might not be perfect but you have to realise it is not a new unit and there is a possibility even after the testing next time you use it might not work anyway.

Cheers

I'm sure you are a great surveyor and this is no knock on you. But I'm finally looking at that really sweet 1934 Ford pickup fully restored I've been dreaming about and I can't thank you guys enough.

chrisr · 16-10-2021, 18:38

i tested our watermaker in a (reasonably) fresh water river recently

firstly, it doesn't harm anything, regardless of what it says in the manual. no difference to a fresh water flush is it ?
secondly, while certainly not a good test, you can get an idea how it's working by looking at the pressure required. eg in sw, we start making fw at about 550psi (operating pressure abt 750psi). in the river water we started making fw at abt 200psi. although this might not be a big help if you're not familiar with the equipment, the manual should tell you at what pressure flow starts

the only problem as far as i can see is mud etc clogging the pre-filter/s

cheers,

Paul L · 17-10-2021, 00:04

Quote:

Originally Posted by chrisr

i tested our watermaker in a (reasonably) fresh water river recently

firstly, it doesn't harm anything, regardless of what it says in the manual. no difference to a fresh water flush is it ?
secondly, while certainly not a good test, you can get an idea how it's working by looking at the pressure required. eg in sw, we start making fw at about 550psi (operating pressure abt 750psi). in the river water we started making fw at abt 200psi. although this might not be a big help if you're not familiar with the equipment, the manual should tell you at what pressure flow starts

the only problem as far as i can see is mud etc clogging the pre-filter/s

cheers,

It depends on the watermaker type. A Spectra is essentially a fixed volume pump, so it should work similarly in freshwater with higher output.
My old Village Marine would way over pressurize the membrane if run in freshwater without readjusting the pressure valve way down from its saltwater setting.

**GordMay** · 17-10-2021, 05:16

Quote:

Originally Posted by Tellie

... as Cheechako mentioned, membranes are relatively inexpensive.
http://marinewarehouse.net/images/Sp...II_mpc5000.pdf

I didn’t see any listing, for the cost of replacement membranes.
➥ Spectra Watermakers

Just for perspective, could someone quantify what “inexpensive” means.
ROUGHLY [NOT a quote] how much should one expect to pay, for a replacement membrane?

**Tellie** · 17-10-2021, 06:48

Quote:

Originally Posted by GordMay

I didn’t see any listing, for the cost of replacement membranes.
➥ Spectra Watermakers

Just for perspective, could someone quantify what “inexpensive” means.
ROUGHLY [NOT a quote] how much should one expect to pay, for a replacement membrane?

Anywhere from $150-$350 for standard non proprietary membranes to $600-$1,500 for proprietary membranes. This would probably be the range for pretty much most watermakers we discuss here on CF. Once we get into the bigger more specialized units on larger yachts even more. It all depends on the size, proprietary, and manufacturer. But usually as with the Spectra discussed above they don't use proprietary membranes. As you know inexpensive is relative. But for a $5,000 to $15,000 watermaker I personally would consider the $200-$350 range inexpensive for something that on average should last around 5-8 years if properly taken care of. Hope that helps.