Watermaker workings and quality. Educate me.

[dgasmd]

Trying to learn a little on how these units are put together, how they work, and product water quality.

I've used and built a pretty good RO/DI unit in the past for a large/complex reef aquarium system, so at least I know how those work, their principles, pre-filters needed/used, product water quality expectations, waste water, etc. What I don't know is how any of this relates to the units used or designed for boats. Since I am assuming the water quality one would expect (assuming equal to tap water at home) is far from 0 PPM, I have no idea of expectations.

So, can someone briefly and in a simplistic way a 4 y.o. can understand talk me through the different stages or pre-filters, pump, membranes, discharge, typical daily outputs, and product water quality?

Thanks in advance.

[delmarrey]

Here's a good article to start with.>>> Marine Watermakers

[dgasmd]

Great. Sort of I was looking for. Unless I missed it when I scanned through it, it does not mention the objective quality of the water. In other words, what do you measure to know the product is good and everything is working well? What range is used to say "this is good product water" vs "pre filters need changing or membrane is going bad, etc.

[TacomaSailor]

We've been using a Spectra 16 GPH system with two feed pumps since 1999. The system has a wire mesh strainer to get the big stuff out and then a 20 micron and 5 micron prefilter.

My wife has been involved in public water supply and quality management for the last 30 some years and is very particular about her drinking water.

Our objective measure is less than 500 ppm measured with a calibrated HANNA TDS1 meter. Our subjective measure is no odd smell or taste.

Our typical ppm readings are 180 - 250 but have drunk water with a TDS reading of 550 ppm with no problems. Frequently we have to run the pressurized watermaker for 10 minutes or so to get rid of the odors before we allow the product water to be piped into the water tank. We have a cockpit valve that allows the product water to be piped over the side with a discharge port that we can reach from the cockpit. We just put a clean glass under the port, gather a sample, sniff test it, test for TDS, and then taste test. Once it passes all those tests we change the valving to allow water into the tank.

Our most common subjective quality complaint is a faint "grassy" odor to the water when the prefilters need to be changed. This can occur in as few as five hours run time in water with lot's of plankton growth or as infrequently as 30 or 40 hours in pristine clean water.

Our worst quality problems have been in Puget Sound in 50 degree water when there was intense plankton bloom. The wire mesh screen would clog in just a few hours run time and the 20 micron filter needed replacement every four or five hours run time.

The ppm TDS increases significantly when we run with only one feed pump. Using two feed pumps generates 120 psi feed water to the Clark Pump but running only one feed pump generates only 95 or so psi and results in TDS of 325 - 450 ppm instead of the normal 180 to 225 ppm.

Other folks I know with watermakers accept tds ppm of up to 600 with no problems.

Our Spectra with two pumps running makes 15 - 16 GPH while using 17 amps of 14.4 current. We have 600 watts of solar panels so have no problem making that kind of power.

While cruising we run the Spectra at least one hour per day, every day to keep it fresh. That means we always have too much water and take frequent showers and wash the decks with fresh water every couple days.

The more you run a Spectra the better it performs so we run it in non-pressurized mode (water is not being forced thru the membrane) for several hours a day if we are running the diesel.

We are still using the original membrane that came with the Spectra when I installed it in August 1999. Other Spectra users I know have gotten even more life out of their membrane.

I've replaced the following components int he 13 years we've had the Spectra:

Feed Pumps
Pump Heads
over pressure switches
Pre-Filter Cannister housings
Clark Pump main body

The Spectra was a great system 13 years ago and is even better now.

[dgasmd]

Wow, these are far greater ppm than I'd guess. My tap water at home is 130 ppm and I consider that pretty bad for drinking. For cooking or washing and other things is a mute point though.
Thanks for the note and opinion/info.

[HeartsContent]

Tacoma, That was an outstanding write up. Thanks!

I would guess that one could use a Brita or other household water filter to get "perfect" water out of what the watermaker puts in the tanks.

Does anyone do this?

[dgasmd]

Brita is one of the biggest gimmicks on the market. They hardly do anything at all. If you have a yes meter, measure your tap water and water from a Brita filter. It may drop 5-10 points max. Huge waste in my book!!

[TacomaSailor]

"I would guess that one could use a Brita or other household water filter to get "perfect" water out of what the watermaker puts in the tanks."

My big complaint about watermaker water is that it has NO taste - after all it is sterile - no biologic material, e.g. virus, microbes, decayed matter, can pass thru the membrane as well as no mineral that would provide some flavor or taste quality.

We've had our watermaker water tested by my wife's water quality lab and it is perfect - but flavorless.

No need for any other filter.

And... a Brita is only good for 10 20 microns and that can't even get past my 5 micron pre-filter.

[Cheechako]

When I bought my catamaran, it had a 1.5 HP 120volt water maker with a very large and complicated control and indicator panel with multiple lights etc. to indicate water quality and status. long story short the unit always indicated water was out of spec.... although it smelled and tasted fine.
I salvaged the Cat pump, valves etc and junked the panel and the 1.5 HP motor. (Got rid of the weight and a Northern lights gen set also!) Then installed the cat pump on one engine with an electric clutch, My system was totally manual: close the needle valve to 600 psi and make water. (it did have a relief valve) Worked fine, if the water tasted good it was good to us.
I dont drink much water as it's distasteful to me... except RO water which I like!

[goboatingnow]

TDS of 500 mg/l or below is generally regarded as suitable for drinking. Most public water is 250 mg/l. It is not recommended you drink water below 100mg/l or at least take supplements. Humans can start to taste salts at concentrations over 500 mg/l. Your body is not designed to drink pure water.

WHO regulations suggest water upto 2000 mg/l can be tolerated( note tolerated, ie third world conditions) . EPA limits are 500 Mg/l or less I beleive , excellent water is between 80/100mg/l to about 350 mg/l. Good water is 350 to about 600.

Dave

[WaterFixer]

Tacoma, Does your Spectra have a UV following? Many of the Spectra 12v Units have them.
Jesse

[Tellie]

That was a very good write up Tacomasailor. But as usual, I just can't leave well enough alone. First anyone that gets 14 years out of a membrane certainly doesn't need my advice on how to take care of their watermaker. 14 years is an extreme rarity, especially since membrane technology is better now than it was 14 years ago. Usually on boat based systems 5-8 years is the norm for a membranes life expectancy on a well taken care of unit. So huge Kudos to you. One thing to clarify for others, it's better to run your watermaker every two days for two hours than every day for one hour. The fact that you run it unpressurized for several hours every few days makes up the difference. But most typical cruisers won't do that. Just curious, when was the last time you did a product flow test? Spectras with the two Shurflo feed pump configuration are rated to produce 13gph, 14-14.5gph is not unheard of but 16gph if accurate may indicate some degrading membrane issues. Also 95psi with one feed pump running points to membrane problems and 120psi is just a tad high with both feed pumps running. None of these pressures concern me a bit considering the age of your membrane, but if these readings are accurate it points to some clogging of the membrane. Again 14 years, I'd say everything is better than I would have suspected. The issue with such high pressures is not the water quality, at 500PPMs no one would know it by tasting it. But the issue is with premature pump head wear. As you've stated above you've replaced a few and you know they are proprietary to a Spectra. I also agree with you on the Brita filters. Salt water membranes filter down to the nano filtration level. A Brita is so far up that scale as to be out of sight. It's why salt water RO requires 700+ psi to begin and Brita relies on gravity to filter very little. People would be better off with a simple replaceable Home Depot charcoal filter plumbed under their galley sink. Watermakers make great water, but once it's dumped into a boats fresh water tank we have no idea what's going on in there.

[TacomaSailor]

While I cruised the Sea of Cortez 2001 - 2004 one of my close friends, boat buddy, and regular snorkling companion was a (at that time THE) factory trained Spectra representative in the Sea. He is the one who taught me most of what I know about the Spectra.

My factory manual says to adjust the high pressure pump shutoff for 120 psi. I have spent considerable time (hundreds of hours) working on and adjusting my system. The phone support I consistently received was a minimum of 115 psi shutoff and 125 was OK.

I have done many flow tests. When new I consistently saw 16.5 GPH product water with 180 GPH bypass water. The last test I did was several years ago when I installed a new feed pump. The product was 15.5 GPH in 48 degree feed water at 120 psi feed shut off and 14.4V at the pump.

Product output is very sensitive to feed water temperature and pump voltage so it is necessary to specify both measurements when reporting product flow.

A close friend, who I've done a lot of cruising with, just replaced his Spectra membrane after 16 years. There was no particular need to replace it but he found a great deal on a new one for $189 and they were leaving just before Thanksgiving for an open ended cruise to Mexico (their 3rd). The old membrane looked fine and was still producing 300 ppm water at 8 GPH in a one feed pump system.

[Tellie]

I probably know your buddy. But a few things have changed a bit since 2004 as Spectra has evolved. The pressure your feed pump runs at is not determined by what cut off pressure you adjust the pressure switch to. If your analog pressure guage is reading 95psi with one pump running it is over pressurizing. On a 10% pump and 40" membrane the pressure for one pump alone should normally be in the 50-60psi range. If it's 95psi it's certainly fighting a blockage somewhere. Secondly, if both pumps are producing their rated pressures turning on the second pump while the first is creating 95psi the pressures would surely climb much higher than the 120psi you stated and they would both be cutting on and off. New cut off pressure settings are now 125psi. You either have a Gulf Stream, a Santa Cruz, or a 380C. Adjusting the pressure switch is different for each unit. Santa Cruz and 380C systems are the easiest. The Gulf Streams could experience seal failures on a improper pressure switch setting. Your buddy with the 180C has an amazing membrane as well. Since Spectra has only been in business since the late 90's he must have one of the early experimental 180C units. Like I said, you guys are doing an amazing job of caring for your units.