DIY Watermaker: Pros & Cons

[Celestialsailor]

Originally Posted by Jsta_Rebel

I'm not too keen on the spectra units.

Can you tell me why?

[SV THIRD DAY]

Before I say more the only reason I feel compelled to correct wrong or misleading information when I see it on a water maker post is because letting it stand uncorrected is what leads to Dock and Chat Room Rumors and they can send innocent cruisers down the wrong path. I see these poor folks all the time. They have a tight budget to start with and then get totally screwed by bad advice when they find out their Ebay pump and motor combination won't work together. Or they didn't match their Pump output to the Membrane correctly and it plugs up after 6 months.

So despite what your are thinking, I don't have a compulsion to be a know it all or smart ass or the guy who can't let something go. (ok I am a smart ass so take that back) I just hate seeing fellow cruisers screwed by bogus information they get online.

Originally Posted by Prior Quote

Hello TickMan,
there is no reason to worry about RPM:
a) You'll probably need a device to increase RPM slowly from zero to full speed. If so then you may run the pump at any RPM between lowest (see manual, something about 700 RPM) and max (1750).
b) the 1800 RPM rating of the motor is a theoretical number. DC motors run faster at 14.7 Volts (when the engine is running and the alternator delivers current) and more slowly at 11.8 Volts (no engine running). Anyway, the difference of nominal 50 RPM do not count in reality.
Neither will you run the pump at 1750 RPM nor will the motor run at 1800 RPM in real life.

Right off that bat you HAVE to worry about pump RPM for a few reasons:

1. It does not hurt the pump to under spin it, BUT the pump's rated output of lets say 4.2GPM is at 1750RPM. The pump output is directly proportional to RPM, so cut the RPM in half and you cut the flow rate in half. Pressure doesn't matter to the pump since it's a positive displacement. It will pump out 4.2GPM at 5PSI or 800PSI.

2. Spinning a pump faster than the rated speed WILL damage the pump, so that's bad.

3. Once you set your needle valve you need to hold the pumps RPM constant or you WILL change the pressure of the system and not be able to hold your 800PSI set point. This is not the case when you are using a dynamic true pressure regulating valve, which will hold the constant 800psi at any flow rate. But most DIY water maker guys are not using a true regulating pressure valve, but a simple needle valve. Not this doesn't really matter for an AC motor, but is HUGE to pay attention to on an engine driven and to a lesser extent a 12v unit where the voltage will sag as you are destroying your battery bank trying to run a energy hog piston pump off a 12v batter bank.

Next
You always start and stop a water maker equipped with a needle valve to create back pressure on the pump with the needle valve open. This way the membranes are never seeing a slam of pressure at Hp Start-up. Pressure slams and dramatic and rapid pressure changes WILL damage or destroy the membrane...bad bad bad. Even more importantly, you don't want the Hp pump to start under load. This is a huge deal because we could be talking about double the start-up Amp draw of the Pump/Motor set-up if you start it under load. You DO NOT vary the RPM of the motor/pump at start-up, that's just not the way it's done on these smaller motors. Why, because that would require using a VFD for an AC Pump or a Voltage Controller on a DC pump. There are NO systems on the market for smaller Boats that vary the RPM of the Motor/Pump, so implying there are will lead people down a bad and expensive mistake path. You start the water maker up with no back pressure and then once running, you slowly close off the needle valve which puts back pressure on the Pump and Membrane housing to make your 800PSI. (this is how it works on a Piston pump. ETDs are different of course)

50RPM is indeed not a big deal, so paring a 1750 Rated RPM Pump with a 1800RPM rated motor isn't going to hurt anything. But why undersize the RPM and give away pump flow if you can help it? The power savings just isn't that great. For example, our 1.0Hp motor runs at 8A 115v AC with 100PSI. Now take it up to 800PSI and now it's using 9.3A. So that 1.3A is not much savings in power but 600PSI to 800PSI can be 20GPH in fresh water production, so don't leave RPM on the system design floor if you can help it.

Originally Posted by Prior Quote

BUT:
The motor from your Amazon link is a 0.5 HP motor.
Now, there is a simple formula for every high pressure piston pump to find out what HP you need.
The formula goes like this

Required Power [kW] = (0.26 * gpm * psi)/475

When we use the specs of your pump:
(0.26 * 2 gpm * 800 psi)/475 = 0.88 kW

0.88 kW equals ~1.2 HP

If you try to run the pump with a 1/2 HP motor neither will it deliver 2 gpm nor will it reach anything close to 800 psi.:

Danger Will Robinson...Danger....
If I had a dollar for every DIY guy that totally screwed himself by trying to match his pump and motor with calculations rather than real life data...well I would eat out more at finer Taco Carts!

Here is some real life what will work piston pump and motor match-ups at 800psi. Tested using the WM series General Pumps.

1/3Hp - 0.5GPM Pump
0.5Hp - 0.8GPM Pump
1.0Hp - 1.6GPM Pump
1.5Hp - 2.3GPM Pump
2.0Hp - 3.0GPM Pump
2.5Hp - 4.2GPM Pump (Or single 1/2 V-belt pulley)

[TickMan]

Hello

Is any one know how to install membrane inside vessel ?
1- I have two SW30-2540, but don't know what possition brine seal position must be , Feed water inlet or Brine discharge outlet ?

Here is anwer from AmericanRO

PHP Code:

Brine seal on membrane faces the 2 port end plug.
Feed water goes to the outside port on the 2 hole plug (NEVER FEED WATER DOWN THE CENTER PORT)
Single hole port is the waste port. 


Everywere I see different possitions, but whcih one is correct ? Here is all different versions

http://cdn1.bigcommerce.com/server70...lmtec-sw30.jpg

http://www.lenntech.com/images/Filmt...brane-draw.jpg

2- Now I have problem to remove it, how to remove membrane from vessel ?

3- Salt a rusty water get ouf of both "new" mebranes, looks at least strage for me. Is it normal, or guys just seelling old ones for price of NEW ?

[SV THIRD DAY]

Here is a link to our Membrane Change Out Procedure:
http://www.cruiserowaterandpower.com...eChangeOut.pdf

You could have to push in on one of the two end plugs which will push the opposite end plug out. Sometimes they do get stuck in pretty good.

Crap coming out of a new membrane....no mate...that is a problem and NOT NORMAL.

[TickMan]

Originally Posted by SV THIRD DAY

Crap coming out of a new membrane....no mate...that is a problem and NOT NORMAL.

Answer from American RO :
No it is not funny that you have so many questions. We a distributor who sell to OEMS & service provider. We do not have the resources, pricing is not for end user, or bs model is not designedto deal with the end user.

There are no manuals because there any several configuration depending on the application / design.

No reason for rusty water, an indication your prefilter is no working correctly. Or is membrane has been opened and sitting around for sometime causing bacterial growth on the membrane.


American RO
859-624-8577 Ph/Fx
americanro@aol.com
FILMTEC MEMBRANE

[SV THIRD DAY]

Originally Posted by TickMan

Answer from American RO :
No it is not funny that you have so many questions. We a distributor who sell to OEMS & service provider. We do not have the resources, pricing is not for end user, or bs model is not designedto deal with the end user.

There are no manuals because there any several configuration depending on the application / design.

No reason for rusty water, an indication your prefilter is no working correctly. Or is membrane has been opened and sitting around for sometime causing bacterial growth on the membrane.


American RO
859-624-8577 Ph/Fx
americanro@aol.com
FILMTEC MEMBRANE

With all due respect and frankness, that is what you get these days when price is the main buying point decision over quality or customer service. Customer service and giving technical support to customers costs money and there is just no way around it. American RO sells their pressure vessels cheaper than we do (ours are $425)...but ours comes with all the customer service you need and want. I couldn't sell mine at their prices AND still give the level of support we do and still be in business. Not to defend their answer, which was somewhat rude, but they are being honest in saying that their business model does not provide time/energy for customer support and technical assistance. It's the classic thing people overlook when calculating how much they can "save" by building their own water maker...customer support isn't all that important until it isn't there.

I'm happy to help so email me whatever you need at Rich@cruiseROwater.com. I'm currently working out of our La Paz, Mexico office so I'm in a much better mood to help since I have a supply of cheap Tacos for the next few weeks!

[Therapy]

Originally Posted by TickMan

Answer from American RO :
No it is not funny that you have so many questions. We a distributor who sell to OEMS & service provider. We do not have the resources, pricing is not for end user, or bs model is not designedto deal with the end user.

There are no manuals because there any several configuration depending on the application / design.

No reason for rusty water, an indication your prefilter is no working correctly. Or is membrane has been opened and sitting around for sometime causing bacterial growth on the membrane.


American RO
859-624-8577 Ph/Fx
americanro@aol.com
FILMTEC MEMBRANE

Originally Posted by SV THIRD DAY

With all due respect and frankness, that is what you get these days when price is the main buying point decision over quality or customer service. Customer service and giving technical support to customers costs money and there is just no way around it. American RO sells their pressure vessels cheaper than we do (ours are $425)...but ours comes with all the customer service you need and want. I couldn't sell mine at their prices AND still give the level of support we do and still be in business. Not to defend their answer, which was somewhat rude, but they are being honest in saying that their business model does not provide time/energy for customer support and technical assistance. It's the classic thing people overlook when calculating how much they can "save" by building their own water maker...customer support isn't all that important until it isn't there.

I'm happy to help so email me whatever you need at Rich@cruiseROwater.com. I'm currently working out of our La Paz, Mexico office so I'm in a much better mood to help since I have a supply of cheap Tacos for the next few weeks!

And where are they really and who are they?
They don't have a good handle on the language.
Communication is key to any relationship.

[TickMan]

Originally Posted by Therapy

And where are they really and who are they?
They don't have a good handle on the language.
Communication is key to any relationship.

Here is their web site FILMTEC MEMBRANE and there what we can see :
Residential and end user customers please call or email for pricing.


So they are selling to end user customers and they didn't tell me in advance, you will not get even manuals and zero support. Honestly I don't need any suport from they, but main problem was membrane seal position, this is where was hard to understand, since here schematic is way far from any other RO membranes.

[Celestialsailor]

Wow!...that post spoke volumes.

[sailorboy1]

I think some of the problem is that everyone assumes a DIY person has the needed skillset, when maybe all they are is cheap.

[Tellie]

Originally Posted by sailorboy1

I think some of the problem is that everyone assumes a DIY person has the needed skillset, when maybe all they are is cheap.

We sailors do have a reputation.

[capn_billl]

Originally Posted by ghaffy

Hello TickMan,
there is no reason to worry about RPM:
a) You'll probably need a device to increase RPM slowly from zero to full speed. If so then you may run the pump at any RPM between lowest (see manual, something about 700 RPM) and max (1750).
b) the 1800 RPM rating of the motor is a theoretical number. DC motors run faster at 14.7 Volts (when the engine is running and the alternator delivers current) and more slowly at 11.8 Volts (no engine running). Anyway, the difference of nominal 50 RPM do not count in reality.
Neither will you run the pump at 1750 RPM nor will the motor run at 1800 RPM in real life.

BUT:
The motor from your Amazon link is a 0.5 HP motor.
Now, there is a simple formula for every high pressure piston pump to find out what HP you need.
The formula goes like this

Required Power [kW] = (0.26 * gpm * psi)/475

When we use the specs of your pump:
(0.26 * 2 gpm * 800 psi)/475 = 0.88 kW

0.88 kW equals ~1.2 HP

If you try to run the pump with a 1/2 HP motor neither will it deliver 2 gpm nor will it reach anything close to 800 psi.

Sorry to say.
I built my WM on my own from scratch. This little motor won't work in a "1st generation water maker" (i.e. plunger pump plus SW30 Filmtec membrane).

SO if I buy this
https://www.pwoutlet.com/AR-XTA1G15E...ta1g15e-f8.htm

It should work?

[Franziska]

Hi,

I am aware that this is an old thread, but I just had a simple thought and wonder if its not a good one.

It seems to be consensus that the pressure water pumps do not last well in seawater or when pickled. Corrosion seems to be the main issue and not operation.

Now my thought is, if its dry, it should have no issue.

So, why not attach it with some high pressure quick release couplings & valves (If that exists with a reasonable pricetag)?
Of course there has to be a release valve close to the pump before it reconnects to the high pressure side, so that you can depressurize the pump before disconnecting it.

So after use you flush or clean the system as usual with freshwater or freshwater with chemicals.
Once that is done you close the valves on both sides of the pump and drain it into a bucket, or you mount the system in a way that it drains into the bilge or overboard.
No need to permanently expose the pump to seawater or pickle solution.

When you are ready to make freswater again, you just plug the pump back into the system, open the two valves and make water.

That should do away with the need to replace those pumps often and make them last much much longer while essentially erradicating the need for a very expensive stainless or bronze pump on such a DIY system.

Or are there any other parts which are expensive and dont last well in the DIY system described by GHAFFY here:
https://www.albin25.eu/index.php/tec...o-s-watermaker

Any thoughts?

One question, if we connect two standart 40" RO membranes, could a cheap system with the pressure water pump increase output over a system with one?

[s/v Thea]

I’ve been using a brass pump (General Pump - T9731B) since 2013, average four months of use a year, pickled the rest of the time. I always flush with fresh water after each use.

[Franziska]

CORRECTION.

Btw. I meant Kaercher style pressure washer pumps not any pressure water pump in my posting above.

Stainless or bronze pumps last well, but the method described refers specifically to the pressure washer pumps which tend to corrode easy.