Watermaker

Water desalination device for marine and home use.

The designs provided here are best suited for temporary (emergency) repairs. The pressures inside the unit may go up to 100 bar, and if anything explodes, it could damage everything around itself, including you. That being said, use these designs at your own risk. If using these parts and modifications voids the warranty, causes you harm and/or damages your equipment, the responsibility lies solely on you (🫵).

Parts

Aside from parts of Schenker Zen 30, here's a list of fasteners, plugs, etc:

- 4 x M6 x 1.0, 70mm titanium socket head bolt

- 4 x M6 x 1.0, 100mm titanium socket head bolt

- 4 x M6 x 1.0, 90mm titanium socket head bolt

- 8 x M10 x 1.5 titanium nut

- 16 x M10 x 1.5 titanium hex cap nut

- 2 x G1/8 plug

- 3 x G3/8 plug

- 2 x 3/8" BSPP ORB to 3/8" BSPP male swivel 90º elbow fitting

- 1 x 3/8" BSPP high-pressure hose

- 5 x M10x1.5 threaded rod 680mm long

- 3 x M10x1.5 threaded rod 690mm long

- 2 x 2.5x65mm EPDM O-ring [inside piston tubes]

- 2 x 5x60mm EPDM X-ring (ideally PTFE-coated) [pistons]

Energy Recovery System (ERS)

Problems & solutions:

- Piston X-rings. These tend to wear out, which leads to nasty noise coming from the clark pump's tubes during operation, as well as low volume of fresh water production, bad output quality, and eventual complete cease of production of fresh water. Solution: print one yourself! The design is scaled down 15% from the size that the ring takes after installed on the piston, and it must be printed using a flexible filament (TPU). E.g.: https://www.o-ring-stocks.eu/x-ring-59.7x5.33-epdm-70-shore-a-black-ors233457

- All five carbon fiber tubes have sharp edges, and it often results in o-rings getting cut when the unit is assembled. One way to improve it is spending a couple of hours rounding and smoothing out the edges of those tubes with something like a nail drill (20,000rpm or higher). But make sure not to make those tubes shorter than they are supposed to be, just take care of the sharp edges.

- It's quite difficult to disassemble the unit. Solution: add 8 nuts paired with washers between Delrin end cap blocks to make it easier to push them away from the central valve.

- It's hard to assemble and properly tighten the large nuts that hold the unit together. Solution: permanently etch thin white lines on all tubes to better see when they're all the way in or not, and make sure the unit doesn't wobble during the assembly process and is completely straight. A skewed clark pump is likely to create friction between pistons and their tubes, and scratch both of them.

- The two 90º high-pressure hose elbow fittings are made out of cheap stainless steel. A couple of months down the road they'll corrode, with bits and pieces falling off and entering the internals of the ERS, likely scratching the piston tubes, pistons, which will inevitably wear down piston X-rings and make the ERS produce loud noise during operation. I'm currently looking into replacing those fittings with aluminum (6061-T6) or G2/G5 titanium: https://ppcfittings.com/products/90-degree-o-ring-boss-o-r-b-swivel-to-male-an-fittings & https://ppcfittings.com/collections/hose-ends/products/copy-of-show-chrome-plated-swivel-hose-ends-mirror-finish?variant=29040944480367

- There are three stainless steel G3/8 sealed plugs inside the left end cap, they'll eventually corrode. Solution: switch to non-metal plugs: https://www.jwwinco.com/en-us/products/3.5-Controlling-venting-sealing-of-liquids-and-gases/Threaded-plugs-Sealing-plugs/EN-746-Technopolymer-Plastic-Threaded-Pipe-Plugs-with-NBR-Rubber-Seal

- Two plastic 3/8" NPT fittings used for input and brine discharge are not bad on their own, but each time you service the ERS and disconnect the hoses, they'll take wear; not to mention require lots of work (tightening/loosening hose clamps & likely using heat gun on the input hose). Solution: switch to 3/8" to 1/2" NPT thread adapters (nylon works great), and then connect hoses to wingnut connectors: https://www.freshwatersystems.com/products/nipple-hex-1-2-x-3-8-mpt-natural-nylon & https://www.freshwatersystems.com/products/shurflo-234-2936-hex-swivel-straight-1-2-fnpt-x-5-8-barb-poly & https://www.freshwatersystems.com/products/shurflo-234-3936-wingnut-swivel-elbow-1-2-fnpt-x-5-8-barb-poly — I use elbow (90º) connector for brine discharge for the sake of making it easier to turn the long screw valve located underneath.

Pump

Just like Spectra watermakers, Schenkers come with a SHURflo series 8000 positive displacement diaphragm pump, the precise model is most likely 8000-943-838. Here's the list of parts: 35-028-01 motor cover, ??-479-00 solid diaphragm drive base, 21-584-00 poly upper housing, 94-385-32 drive assembly.

Problems & solutions:

- It's notorious for 3 small diaphragm valves to break, which results in stunted flow and pressure, eventual inability to produce fresh water. The solution to that is upgrading the pump with reinforced diaphragms from a different pump model, e.g. https://tweetys.com/shurflo-94-232-06-fresh-water-pump-valve-assembly.aspx (notice the little “cross” in the middle of every diaphragm — that's the reinforcement we're after)

- The little white check valve wears down and eventually falls out. Solving this requires a replacement, and there happen to exist options — same exact valve, but different materials: 94-374-16 (EPDM), and 94-374-05 (Celcon/Viton), 94-374-09 (Celcon/EPDM), etc; anything with Celcon is currently my choice, since wear resistance is the main problem for this part. The replacement process involves removing the pressure sensor and re-assembling the 5-part mechanism. It's important to note that the watermaker is capable of producing water without it, but running the pump that way will likely consumes more energy and put more stress on the motor.

- Plastic barb fittings can deform from the heat if the unit operates for a long period of time, and they also take a lot of scratches due to change of hoses and not suitable for handling pressure of overtightened hose clamps. Solution: replace them with 3/8" to 1/2" NPT (nylon) thread adapters, and then connect hoses to wingnut connectors: https://www.freshwatersystems.com/products/nipple-hex-1-2-x-3-8-mpt-natural-nylon & https://www.freshwatersystems.com/products/shurflo-234-2936-hex-swivel-straight-1-2-fnpt-x-5-8-barb-poly

- Changing the pump requires cutting wires. Mod it to use 2-pin Deutsch connectors, similar to https://www.mniboats.com/BALLAST-KING-W-DEUTSCH-CONNECTOR-316-SS-DRIVE-S-p/190157.htm

- The fan that comes with it is too small and not waterproof. Use a 3D-printable funnel adapter and replace it with https://noctua.at/en/nf-f12-industrialppc-2000-ip67-pwm

- The pressure sensor is vestigial, it only makes the pump more noisy and weigh 30g more, take up more space. Remove it and use “Watermaker - Pump - Bypass Cover.3mf” to cover the opening, as can be seen on a bypass variant of this pump: https://sprayersupplies.com/8006-543-250-shurflo-a7527350

- The large 6 stainless steel screws will seize inside the metal base. Re-assemble the pump covering those screws in something like ASC-I compound: https://www.parktool.com/en-us/product/anti-seize-compound-asc-1

- The controller box is attached to the pump, which requires below-waterline installation; if anything leaks, there's a risk of that box getting submerged. Solution: move it away from the pump, reposition close to the control panel.

- The external pressure switch gets in the way when servicing the pump. Solution: move it closer to the ERS, ideally where it can't get submerged, or even better — modify the sediment filter to have a thread for that sensor to reduce the amount of hose clamps and barb adapters required for the switch.

- The motor in these pumps is brushed, it's noisy and produces more heat, lives about 4–5 times less than brushless pumps. It can in theory be replaced with something like Seaflo SFDP1-018-120-31, or SHURflo 8075 with a voltage booster/regulator, tweaked to match the original pump's flow and pressure.

Raw Water Strainer