Page 1 of 1


Posted: Sat Aug 12, 2006 6:05 am
by northerncat
i was looking at a site the other day about making your own watermaker, a bloke had used a high pressure pump from a waterblaster and puchased a membrane added a couple of 20 and 5 micron prefilters put a pump in line before the pump and made 20 litres of fresh water an hour for te grand toatl of 800$ ill try to find the site again to post the link the only reason i post this is that i want a watermaker but the 12grand that spectra want is to much so i have been mulling the idea over in my head and am thinking of looking into it a bit more, also to check that the water was pure enough he had some kind of electrical solenoid in line that woud close a valve and pump the water overboard if the water salinity hit a point that it would conduct electricity, i thought that all this was pretty clever and am feeling inspired



Posted: Sun Aug 13, 2006 10:59 pm
by northerncat
a great link to a site withg a make your own watermaker instructions i am very interested in this as i dont have the 12000 that spectra want and also believe that the components could be purchased relatively cheaply


is anyone else interested in looking into this


Posted: Tue Aug 15, 2006 12:11 am
by 44c
Looks like a good idea. Makes you wonder how much profit margin Spectra and the others have doesn't it?


Posted: Tue Aug 15, 2006 3:21 am
by Smooth Cruiser
At the end of the day they are fairly simple things and no reason you couldn't build it cheap if you can get a membrane. To prolong the life of the membrane you can go even finer in the pre filters - I use a 10 micron then a 1 micron filter.

The "professional" water makers have a lot of electronic bits attached - mostly to stop the high pressure pump running if something fails - no feed water or whatever - so you want to know that your system is robust - or be prepared to replace high pressure pumps. Having said that - mine has never cut out.

The circuit you describe is exactly how mine works - a low pressure pump feeds the pre filters, with a differential pressure reading across the filters to show when they are blocked. This low pressure filtered water then feeds the high pressure pump, the high pressure water feeds the membrane. There is a differential pressure reading across the membrane too. Then just the piping to remove the brine and the fresh product. The brine outlet has a screw valve which you brin the pressure up with and which starts pushing the water through the membrane rather than bypassing - the higher the pressure the more water is pushed through the membrane.

All fairly simple if you can get all the bits. Mine is all hidden away in cupboards anyway so the finish quality isn't that important.

Good luck whichever way you go.


Posted: Tue Dec 12, 2006 12:41 am
by steve-l

The link for seems to have dissappeared off the web altogether (can only get first page from wayback).

Did you happen to get all the info on this one?

Steve and Cheryl


Posted: Fri Dec 15, 2006 11:46 pm
by admin

I have been approached to place this on our board for those interested. This is not and endorsement of this product in line with the 'Leagl Stuff' of this Forum, just listing of information from the vendor for your information.


50l/hr Seawater Desalination System

Solar Power and Pumps are delighted to offer the Seawater Desalination System manufactured by a global leader in High Turbidity Water Treatment and Gray Water Treatment.

Technical Specifications:
1. Item:
> Seawater Desalination System
> Size 60 x 50 x 95 cm
> Weight 80 Kg
> Power consumption 1200 Watt

2. Capacity flow rate:
> 50L/Hr or 1200L/day

3. Raw water:
> Pacific Ocean clean seawater.
> TDS 35,000 ppm. at 25 degrees C.

4. Output: Potable water (after desalination).
> TDS < 600 ppm.
> This water is suitable for all domestic use.

Detailed water results:
Product water TDS: < 600 ppm
Product water flow rate: 50 L/hr at 25 degrees C.
To meet the above conditions, the 10μ filter and 5μ precision filters are used. Seawater R.O. system uses two of 2.5”x21” of Seawater R.O. membranes model SW-2521. For maximum efficiency the raw water should meet the following:
Turbidity : 1 NTU
SDI: 3-4.

5. Main Parts:
a. Booster Pump
b. 3 Pressure Gauge
c. Filter 2.5”x 10” (10μ)
d. Filter 2.5”x 10” (5μ)
e. Main Pump P211A-3100
f. 2 R.O membranes
g. 2 Flow Meters
h. Regulator
i. Frame (Carbon steel painted)

6. Payment Terms:
Retail price is $9,000.00 GST exclusive
Price does not include delivery charges
50% of the total system value payable as deposit
50% to be paid on delivery

Solar Power and Pumps
27 Willowie Crescent
Capalaba Qld 4157 Australia
Ph. 07-3823-3735. Fax 07-3823-2802. E-mail

Edited to add two photos of the unit and a schematic of the operation. (Smooth Cruiser)



Posted: Sat Dec 16, 2006 1:13 am
by steve-l
Call off the possee Sean

Link suddenly started working again , bit like most things on boats. I hear x-files music.

Steve and Cheryl


Posted: Sun May 27, 2007 3:50 am
by 44c
At the boat show we saw a portable reverse osmosis unit on a small trolley. 30l/hour, powered by a 4 hp lawn mower engine. 35 kg on the trolley, and $3500.00. It's here:

Their website -

Check this out too -

It's the same watermaker without the Briggs&Stratton, runs on AC, can be powered by a 2000w invertor.


Posted: Sun Jan 13, 2008 7:49 am
by Jim
Hi all, some time ago I bought a Offshore Marine Labs. Sea Quencher SQM200 desalinator. (200 gallons / day) I paid AUD $2035 landed which was a good price. It was a few years old but never used. While I was moping around a while ago with malaria I thought I would rig it up and see if it worked. As I didnt have a feed pump I connected it to the garden hose. It did work, well sort of. It would only pump 200psi instead of 850 plus. I checked the motor to make sure it was 12v and not 24v, the HP pump inlet and outlet valves and I wasn't sure about the gauge. Then out of total frustration I went and read the instruction manual. Hello!!. There was a couple of lines that leaped out at me.

"Every fluid has an inherent potential that is directly related to the type and amount of solids in solution. This potential, referred to as osmotic pressure, increases in proportion to relative concentration of a solution. A concentrated solution, therefore, has an osmotic pressure that is higher than that of a pure solution". Thus ends the lesson.

I then grabbed an empty thinners drum and bolted for the boat ramp to get some salt water or "a concentrated solution", hooked it up to the pump and whamo, 850psi. It worked. The water tasted a bit like bore water but without the charcol filters connected that was to be expected. I was a much happier camper.

I was painting the watermaker cupboard today which reminded me of this, and there is SFA on TV tonight.


I have the one with the long membrane. It fits neatly into the back of the cupboard with the pump in front for easy maint.


Posted: Sun Jan 13, 2008 8:15 am
by northerncat
mm i love the taste of thinners too