DIY Watermaker

[Tellie]

Originally Posted by thatboatguy

Hey Rich! I've already posted those links but thanks for the plug.

Everybody this is Rich Boren, my partner in crime.

George

Oh you are THOSE two guys
I remember the Frankenmakerthingy. I followed that awhile back. If I remember correctly my wife ordered some things from Rich online about two years ago. You guys did a great job putting those two units together. When I referenced, in an above post, that people should research online other people who have built their own WM I was thinking the Frankenmaker as one of them. Last I remember George that yours wasn't quite yet finished. Hows that coming along?

[thatboatguy]

The MK II is coming along nicely! Thanks for asking. It has to be "done" by November 21 because that's our shove off date... send me energy.

George

[Tellie]

Originally Posted by thatboatguy

The MK II is coming along nicely! Thanks for asking. It has to be "done" by November 21 because that's our shove off date... send me energy.

George

ENERGY ENERGY ENERGY ENERGY...

[rebel112r]

I am building my own system and have a complete SR sytem..I will be selling what I don't use..Such as, pressure vessels[3 @about 20 inches], 110vac 1 1/2hp Baldor motor w/cat pump,110vac gorman rupp feed pump, very large Sea Recover commercial filter housings 1 an oil separater the other a regular filter housing.Sea Recovery electronic control box...etc

[svcattales]

Originally Posted by svcattales

This is an update of my previous posts on DIY watermaker with pics of installation.

I built a 12 Volt watermaker from plans I bought on Ebay. My unit is driven by a 1/3HP DC motor and it is directly coupled to the high pressure pump. Designed output is 6.5 gal/hr with a power draw of 27 amps. With a bigger motor (1/2 HP) and different pump configuration you can get 8.6 gal/hr at 39 amps. I decided to go with the smaller capacity since it meets our consumption needs for running the system at least once/week. Also, I can support the lower power draw with solar and wind power without running diesel.

My system is complete except I haven't installed the membrane in the pressure vessel yet since I won't be using the system until I start cruising again in December. I did check out the pump/motor and pressurized system to working pressure of 800 psi. I can't comment on performance until I start cruising with it.

The plans were pretty good and there was a complete parts list along with web addresses and prices for all major components. The designer advertises a complete cost of $1,675, but I spent about $1,900 due to an upgrade and price increases on components. Despite having good plans, construction was a time consuming project and required lots of hunting for various plumbing connections, hoses, two-way valves, high pressure hose etc. This was more than a weekend project so if you don't have time to devote to it, you may be better off buying an off-the-shelf unit. The big pluses for me were a total custom installation that used up very little of my storage space and low intitial cost. The other benefit is the availability of all compontents/spare parts without the high cost of single source parts.

The designer was Bob Benglar and his email is benglar at tampabay dot rr dot com.

Pics of my installation:

I installed the membrane this week and gave the new watermaker a good test.

As I closed the pressure valve, product water started flowing sooner than I expected. The designed output was 6.5 GPH at 800psi, but I was actually getting 10 GPH at 550 psi. I tested the product water with TDS meter and it had less than 150 ppm dissolved solids and it tasted great. I increased pressure to 800 psi momentarily to check my high pressure connections and product flow rate went off the scale (above 12 GPH). The DC motor drew 28 Amps when the pump was putting out pressure which was about 1 amp higher than advertised.

I'm not sure whether this good performance is due to my most excellent installation or whether the salinity in Tampa Bay is significantly less than ocean salinity. The Bay water tastes the same to me and burns my eyes like the ocean, but I'm sure salinity is lower by some degree. Also, water temp is still 85 F so that would account for higher output too. I guess "the jury is still out" on performance using ocean water at more moderate temps, but at least I'm sure I will be making rather than carrying water on our next cruise.

[Therapy]

Originally Posted by svcattales

I'm not sure whether this good performance is due to my most excellent installation or whether the salinity in Tampa Bay is significantly less than ocean salinity. The Bay water tastes the same to me and burns my eyes like the ocean, but I'm sure salinity is lower by some degree. Also, water temp is still 85 F so that would account for higher output too. I guess "the jury is still out" on performance using ocean water at more moderate temps, but at least I'm sure I will be making rather than carrying water on our next cruise.

Congratulations.

[thatboatguy]

Originally Posted by svcattales

I'm sure I will be making rather than carrying water on our next cruise.

Outstanding!

George

[rebel112r]

It certainly is satifying when things work....mine still a project, making mounts for pressure vessel and pressure pump, be up and running before spring...

[Tellie]

Originally Posted by svcattales

I installed the membrane this week and gave the new watermaker a good test.

As I closed the pressure valve, product water started flowing sooner than I expected. The designed output was 6.5 GPH at 800psi, but I was actually getting 10 GPH at 550 psi. I tested the product water with TDS meter and it had less than 150 ppm dissolved solids and it tasted great. I increased pressure to 800 psi momentarily to check my high pressure connections and product flow rate went off the scale (above 12 GPH). The DC motor drew 28 Amps when the pump was putting out pressure which was about 1 amp higher than advertised.

I'm not sure whether this good performance is due to my most excellent installation or whether the salinity in Tampa Bay is significantly less than ocean salinity. The Bay water tastes the same to me and burns my eyes like the ocean, but I'm sure salinity is lower by some degree. Also, water temp is still 85 F so that would account for higher output too. I guess "the jury is still out" on performance using ocean water at more moderate temps, but at least I'm sure I will be making rather than carrying water on our next cruise.

It's always because of your most excellent installation that things work so well.
What size membrane are you using? I'm guessing a SW2540 ?
Also a membrane will start making water at lower pressures but you need to remember that the extra pressure helps flow. Keeping the pressure around the 550psi mark will reduce the flow and perhaps lead to earlier failure of the membrane. I've run across this a few times with owners of home built units and manual units that were driven from 12V motors. The owner thinks he's saving amps by lowering the pressure and wondering why he's replacing membranes a lot sooner than he should.
Temperature and salinity do play a role in production as you state, but measurable small. Salinity becomes important when going from high content to little content. This can happen when approaching river mouths and bay inlets. Watching your manual pressure gauge is very important. It is not unusual to damage a membrane during this change.

PS, post pics

[svcattales]

Originally Posted by Tellie

It's always because of your most excellent installation that things work so well.
What size membrane are you using? I'm guessing a SW2540 ?
Also a membrane will start making water at lower pressures but you need to remember that the extra pressure helps flow. Keeping the pressure around the 550psi mark will reduce the flow and perhaps lead to earlier failure of the membrane. I've run across this a few times with owners of home built units and manual units that were driven from 12V motors. The owner thinks he's saving amps by lowering the pressure and wondering why he's replacing membranes a lot sooner than he should.
Temperature and salinity do play a role in production as you state, but measurable small. Salinity becomes important when going from high content to little content. This can happen when approaching river mouths and bay inlets. Watching your manual pressure gauge is very important. It is not unusual to damage a membrane during this change.

PS, post pics

Tellie,
Thanks for the advice on pressure. My membrane is a SW30-2521 which is rated for 300 gal/day or 12.5 gal/hr. My flow meter only goes up to 10 gal/hr so I don't really know the actual flow when I peg the flow meter at 800 psi. Can I damage the membrane at 800 psi if I'm pushing more than the 12.5 gal/hr limit thru it? Maybe I'll need a flow meter that goes up to 15 gal/hr so I can see what's really happening?


Therapy, That Boat Guy and Rebel,

Thanks for the compliments. It was pretty scary running the WM for the first time after many hours of work, head scratching, searching for plumbing connections, and spending all my "boat bucks" on one toy. Seeing it really work, however, was PRICELESS.

[s/v Jedi]

Tellie,

It is my understanding that flow decreases when pressure increases. That leads to better cleaning action at lower pressures, not at higher pressures. I might read it wrong (me is stupid with English) but you seem to indicate that high pressure cleans the membranes better??!!

Also, a RO engineer who explained me everything told me to adjust pressure for rated product flow without going over the maximum pressure for the membrane. So, if the membrane is rated for 20 gph at 20 deg. Celsius water temp, you correct that figure for your water temp and adjust pressure to get that product flow, even if that means a lower than normal pressure.
With fresh water input, I get full flow when the pressure is less than 200 psi. I think it would hurt the membrane when I take the pressure up to 800 psi.

ciao!
Nick.

[thatboatguy]

I've been under the impression that Jedi's description is correct. But as I have mentioned previously I don't consider my education complete on the subject. My instructions (put together from various sources) was to reduce pressure in brackish water to achieve design product flow.

Also, since there is no pressure bypass on the pump, and water does not compress (at least for practical purposes here), the flow rate would be dependent on pump RPM, not pressure at the vessels. Obviously at higher pressures more water will be processed into product so somewhat less scrubbing flow will result at higher pressures.

George

[Tellie]

Oh crap, good questions and I did make it confusing and did not word it well. But there are a lot of variables in the answers. This is where when building your own it becomes a bit muddled. Though the principals are the same, what parts are selected and how you regulate pressure becomes important. Pressure does not equate into cleaning but rather flow does. Think of sidewalk pressure cleaners as an example since the pumps work the same to illustrate the first principal. You can buy a $200 1/3hp electric version at Home Depot that creates 3000psi at rated RPM. You can also buy a $2,000 18hp gas model that creates 3000psi at rated RPM. The difference is in how much volume or flow the two can generate at 3000psi and how much work can be done by either. The first may only flow less than a gallon a minute where the larger unit can flow 5 gallons or more a minute. The difference is not in RPM or pressure but in volume or flow. RO membranes are a cross flow item. Unlike a filter where all the water passes through it, a membrane is designed for most of the water to flow over the surface of the membranes sections and to be passed out as discharge. Keeping the math simple. For every ten gallons of water that passes over a membrane one gallon is worked through the membrane under pressure and comes out as fresh water. The other nine gallons flow over the membrane surfaces washing away the higher concentrate of brine and hopefully any other foreign particles that find their way in as overboard discharge. So if your watermaker is making 6gph you should be discharging 54gph overboard. This is where choosing the right pump, how it is driven and matching it to the right membrane size becomes critical. My original point I was trying to make is when it comes to 12V driven motors owners have tried to regulate the pressure by slowing down the motor with variable speed drive type devices and turning up the pressure with the pressure valve hoping to save precious amps. This will decrease the flow thus the cleansing effect leading to premature membrane clogging and failure. Most pumps suitable for home built watermakers will/should run at a close designed constant of 1750rpm to deliver their proper flow and pressure.

[s/v Jedi]

Tellie,

Okay, that is exactly how I understand it. We pump 180 gph through the system and with the two membranes plumbed in series (2nd membrane gets 90% of the flow of the first one) we are rated for 40 gph total product which is just a bit more than 10% for each membrane.

About temperature: that makes a big difference, at least I would call it big. Our 40 gph rating is at 25 deg Celcius. With water 30 degress C like we have here, the rating should be divided by 0.85 to correct it, which brings it to 47 gph. That's almost 20% more. The water here is even warmer sometimes, like 32 deg C and we have seen 50 gph at times. (this is not a DIY watermaker)

cheers,
Nick.

[thatboatguy]

So Nick,

What do the instructions that came with your watermaker say about brackish water operation? Are you to scroll down pressure until you achieve design product output?

What make/model are you using.

George