My Quest for Water - Engineering build on a RO system

[theller]

Some of you may have seen a few of my posts, but a little background to start this conversation is required. I am a mechanical engineer, with a background in software development. I am turning 30 now and have just started my professional career after long delays of education, life and debt. I want to start my professional life living on a boat and using it to move from job to job taking advantage of the coasts.

In pursuit of this ideal, I have realized this: The cost barrier to entry is way to damn high for cruising. Not the boat, there's plenty of cheap plastic boats for anyone willing to put the sweat into getting it sea worthy, rather every other cost is high.

Part of my goal, as an engineer, and a man on a limited budget is to bring those costs down. My first target is water. Its absolutely essential and a ready supply at low to no costs (I can imagine) makes all the difference living aboard and cruising.

Most systems I have seen run in the ball park of $2500 to $3500. In researching RO filters and the system requirements, I believe this to be whole heartedly over priced.

I intended to build a system and I would like to sell it in the future. My price point objective is $1000 to $1500. I intend to construct with components and parts readily available through commercial suppliers (McMaster Carr) and to use low cost electronics that are viable, capable and replaced at low costs as well as fully rebuildable at sea.

To accomplish this, I have several perspectives that I would like to vett with the community.They are listed below. I would like to hear input back from the community.

1. 150 PSI RO filters.

Currently, I see these types of filters priced in the $80 range with housings around the same prices. Their capacity far exceeds demand (125GPD) and waste water rate is around 5:1. Has anyone used these or had failures with them?

2. Non food grade water pumps.

I know this sounds nutty, but the water is hitting a RO filter, you could run the water through an oil lubricated pump and not have a problem. It raises the issue of contamination due to filter failure though, which I will address next. This is a primary cost saver.

3. contamination detection

Two methods will be used for this, conductivity readings and pressure faults. Using a secondary tank, all clean water will find its way here first. Conductivity will be checked and the software will test this before allowing the low pressure discharge pump (food grade) to move the water to the holding tank.

There will be a light check valve on the clean water output, this will allow a pressure gradient post filter. This pressure gradient from input pressure to output pressure will indicate the health of the filter. A increase in gradient indicates filter clogging, a decrease in gradient (severe) indicates a filter failure.

The conductivity test and the filter failure test will shut the system down and prevent pump out to the primary holding tank.

4. Non self priming high pressure pump.

pre pump, post pump system.
There will be a small pre tank and post tank. Pre tank will have a low cost, low pressure pump capable of self priming and pumping to the pre-filter then to the pre-tank. This allows a non self priming pump to be used, which has a much lower cost. Pressure gradients across the pre-pump will be again used to check for pump and filter failure as well as prevent run-dry on the high pressure pump.

5. Arduino Logic controller -
These little buggers are cheap, but come as a raw board. I can most likely get a system with enough inputs and outputs to run this on and the requried sensors for under a $125. The boards can be replaced completely for $65 and the controller logic chip for under $20. This will require a sealed dry box for the electronics to protect them from the elements.

6. Recommended secondary water tank
My recommendation would be a primary fresh water tank and secondary freshwater. The secondary could be 10-15 gallons. The system should be able to supply 150 gpd, roughly 6 gph. The secondary tank could be rigged with water level sensors and the system could be setup to run automatically for a low cost. This would allow the user to fill their primary tank manually and then run high consumption devices (e.g. shower) off of the secondary. This would provide the safety net between the primary and secondary water tanks.

The goal is $1200 for a final product to a customer (Us!).
Complete electronics rebuild for $200
Complete pump rebuilds for $250
Full Filter replacement, $120 (RO:$80 pre-filters $40)

I want anyone with a screw driver to be able to rebuild at sea.

Thoughts?

[sailorchic34]

Ah, the 150 psig RO units (amazon/ebay) are for use with fresh water, not salt water. Salt water RO needs about 800-900 PSIG for filtration. Thus the more expensive media and pump.

For RO with salt you would need a $100 pressure sprayer pump from the hardware store, then replace the engine oil in the pump with mineral oil. Some have built cheap RO units that way.

Myself I just use tap water, which is cheap in the US. RO in my mine is a bit high maintenance for my taste.

[theller]

I am not speek of the ebay units. Haven't even looked at them.

The units are cited as being brackish water applications.

[onestepcsy37]

Your quest to build a low cost RO interests me and others on this forum. Hopefully, one day you might provide us with a list of off the shelf parts and assembly instructions.
But if you are interested in saving money you might look elsewhere. We have found that it costs less to buy water than to make it. And when you stop to work and earn money you will most likely be in some busy dirty harbor where you would not want to process the water you are floating in.

[Dsanduril]

The osmotic pressure of seawater is ~26 bar (~382 psig - dependent on temperature and salinity). In order to "reverse" osmosis you have to have a pressure greater than the osmotic pressure of the fluid to be treated. So, you will have to be above 382 psig. No 150 psi housing or membrane will work for salt removal from seawater. Current designs require ~800 psig (2x the osmotic pressure) to operate. If you could get the pressure factor down to 1.5x or 1.2x that would go a long way to reducing costs. But then there are lots of companies (some with significant budgets) trying to do the same thing.

Would love to see a cheaper solution, but first you have to go back to the engineering basics.

[Sand crab]

A member here manufactures and sells his own design of desalinization units. They are more money than your project but cheaper than Spectra. Looks real nice. What is his name?

[a64pilot]

Originally Posted by Sand crab

A member here manufactures and sells his own design of desalinization units. They are more money than your project but cheaper than Spectra. Looks real nice. What is his name?

Rich Boren, Cruise RO watermakers.

His unit and a Spectra, are significantly different in approach and design, but both.
do make water. The cruise RO is a high volume, energy intensive AC machine which
requires a generator. The Spectra is a low volume, very energy efficient DC machine.

[travellerw]

I posted a while back that the water maker market is set to change next year. The Spectra patents run out in January 2015. After that, their clark pump will become fair game..

Quite frankly.. If I was still pursuing the "American Dream" I would be using my suppliers and contacts in China to copy what they could and redesign what they couldn't. Pretty sure I have suppliers that could manufacture a Spectra clone and hit a retail cost of $1250 - $1500, even using North American membranes.

My recommendation would be to look at the Spectra patents.. They are well written and detail everything. Their system is not complex and could be easily copied. You just can't sell it for profit until after the patent expires.

[Sand crab]

Originally Posted by travellerw

I posted a while back that the water maker market is set to change next year. The Spectra patents run out in January 2015. After that, their clark pump will become fair game..

Quite frankly.. If I was still pursuing the "American Dream" I would be using my suppliers and contacts in China to copy what they could and redesign what they couldn't. Pretty sure I have suppliers that could manufacture a Spectra clone and hit a retail cost of $1250 - $1500, even using North American membranes.

My recommendation would be to look at the Spectra patents.. They are well written and detail everything. Their system is not complex and could be easily copied. You just can't sell it for profit until after the patent expires.

An untested unproven design from China would put a lot of people off no matter what the price.

[avb3]

Originally Posted by Sand crab

An untested unproven design from China would put a lot of people off no matter what the price.

Perhaps, but what parts other than the membrane are important that it matters that it come from China? Pump? I can't think of much else, and the pump could be sourced from a reliable Chinese manufacturer. They do exist... think Apple.

[travellerw]

Originally Posted by Sand crab

An untested unproven design from China would put a lot of people off no matter what the price.

Yup... this is the perception of many people.. I buy tons of products from China that are quality and well engineered. I have also been to many of the plants and seen my products coming off a line right next to a line making a big brand name product. Its an absolute fact that the majority Yamaha small engines are now made in China by Linhai and has been this way for over 10 years. Linhai is responsible for not only manufacturer, but engineering as well.

The key is to make sure you pick manufactures that won't substitute anything you spec'ed and has quality control engineers. The Chinese are notorious for skipping steps if not monitored..

I would also argue the "untested, unproven design" comment. The patents are very clear and a monkey with a lath and milling machine could turn out a Clark pump.

I would have no problem betting a bottle of rum that you will see a competitive product (with chinese manufactured parts) on the market by January 2016 at a much lower price.

[Sand crab]

Originally Posted by travellerw

The key is to make sure you pick manufactures that won't substitute anything you spec'ed and has quality control engineers. The Chinese are notorious for skipping steps if not monitored.

Yup. The monitoring is the key which is why my iPhone works perfectly. Still a watermaker is so crucial that most cruisers would be hesitant I think. I'm not bashing China because I/we already by lots of stuff from there but I do try to get goods made elsewhere. where possible. I want to spread my wealth around the globe. LOL. But good luck in your new venture.

PS I like Myers rum.

[MYTraveler]

One of my water makers failed. Since it is wholly-redundant and costs about $10G to replace, I am going to replace with something different this time. In exploring alternatives, I realize how simple the entire system is. The only complexity is the controller, and controlling with an Arudino would be trivial. I do think you need 800 psi, and 600 - 800 gpd, but I believe that can be achieved for less than $2500. PM me if you want me to pay for your prototype.

[travellerw]

Originally Posted by Sand crab

Yup. The monitoring is the key which is why my iPhone works perfectly. Still a watermaker is so crucial that most cruisers would be hesitant I think. I'm not bashing China because I/we already by lots of stuff from there but I do try to get goods made elsewhere. where possible. I want to spread my wealth around the globe. LOL. But good luck in your new venture.

PS I like Myers rum.

Nope... Like I said, I'm done chasing the "American Dream".. Just went into contract on my cruising boat and am unloading and untying from land life.. I will leave this venture to some one else (again... Ahem.. SV Third Day)...

[travellerw]

Originally Posted by MYTraveler

One of my water makers failed. Since it is wholly-redundant and costs about $10G to replace, I am going to replace with something different this time. In exploring alternatives, I realize how simple the entire system is. The only complexity is the controller, and controlling with an Arudino would be trivial. I do think you need 800 psi, and 600 - 800 gpd, but I believe that can be achieved for less than $2500. PM me if you want me to pay for your prototype.

Personally I think a better option than the Arduino is the HB 1.0... Instead of using a controller, simply install valves and do everything manually (human brain 1.0). Much more reliable and cheaper..