Watermaker Parts, Membranes and Service in Thailand: What Wears, When to Change It, How to Order
A watermaker that is looked after will make water for a very long time; one that is not will be making excuses within a season. The difference is four consumables, a few hours a year, and knowing what to order before you need it. This guide is the parts-counter view of watermaker ownership in Thailand: what wears, when it is changed, how to read a part number, how a membrane is swapped, how a system is stored, and how we supply all of it from here.
Looking for a part now? Every current Spot Zero and SeaXchange service part is in our watermaker parts section, searchable by the new Spot Zero part number or the old nine-digit 2524… number. Not sure which one? Send a photo and the system serial number by LINE @drakeco or WhatsApp.
On this page
The four things that wear
1. Pre-filters
Before seawater reaches the high-pressure pump it goes through a sediment pre-filter — on SeaXchange systems a 25-micron stage 1 and a 5-micron stage 2 cartridge in the short double housing, or the single 5-micron commercial pre-filter in the 4.5 × 20 in housing. In Thai harbours, with silt after rain and plankton in the warm months, this is the part that gets used up fastest. Change it when the pressure drop across the housing rises, or when the system tells you to. A starved pump cavitates, and a cavitating pump is an expensive part to replace for the price of a cartridge.
Fresh-water purifiers are different. Their pre-filter has to remove the chlorine and chloramine that marinas dose into their water, because chlorine destroys a reverse-osmosis membrane. Spot Zero’s doublestack pre-filter does that with carbon and oxidiser media as well as sediment stages, and it is changed on hours — 100 hours on the Mobile Pro Mini, 10,000 gallons on the Mobile Pro — not on how it looks. A carbon cartridge is finished long before it looks dirty.
2. Membranes
The membrane does the work. Seawater elements come in two standard sizes — 2.5 × 40 in (2540) in long pressure vessels and 2.5 × 21 in (2521) in short ones — and a system’s capacity is set by how many it runs: one for 600 gallons a day, two for 1,200, three for 1,800, four for 2,200 on the SeaXchange range. Purifiers use larger fresh-water elements: 4 × 40 in (4041) in the long vessel and 4 × 21 in (4021) in the short one, and the Mobile Pro Mini element in the mobile units.
Seawater membranes are replaced on condition: when the product-water TDS climbs and the flow falls and a chemical clean does not bring them back. Treated properly — fresh-water flush after every run, pickled for lay-ups — they last for years. Each change takes a seal kit: the brine seal on the element and, on SeaXchange vessels, three end-cap O-rings, which is why we list the O-ring kits next to the membranes.
3. Fresh-water flush cartridge
Every automatic system flushes the membranes with fresh water when it stops, so they never sit in seawater. The flush water passes through its own carbon cartridge (SeaXchange freshwater flush filter) to strip chlorine from the tank water first. It is a small cartridge with a big job; change it with the pre-filters.
4. Chemicals
Two bottles cover almost everything. Membrane chemical cleaner — an acid stage for scale and an alkaline stage for biofilm — is used when flow drops or pressure rises and a flush does not recover it. Membrane storage solution (preservative, or “pickling” solution) is used for any lay-up longer than a month. Purifiers add a bacteriostatic remineraliser on the product side, which puts a little mineral content back and keeps the tank sweet.
Service intervals at a glance
| Part | When | Notes |
|---|---|---|
| Seawater pre-filters | On pressure drop or hour reminder; often every few weeks in silty harbours | Keep two sets aboard |
| Purifier pre-filter (mobile) | 100 h (Mobile Pro Mini) / 10,000 gal (Mobile Pro) | Carbon is spent before it looks dirty |
| Fresh-water flush cartridge | With the pre-filters | Protects the membranes from tank-water chlorine |
| Seawater membranes | On TDS and flow, after a clean fails | Years, with flushing and correct storage |
| Purifier membranes | 500 h (Mini); 1,000 h or 100,000 gal (4041); or when product is < 85 % cleaner than feed | Spot Zero figures |
| Membrane storage solution | Lay-ups over one month; renew every 3 months | Circulate with a chemical pump, max 30 psi |
| Pump oil | Per the system manual | Sight glass on SeaXchange high-pressure pumps |
How to read a watermaker part number
Spot Zero re-numbered its catalogue. The current numbers are two letters, two letters and four digits — FI for filters, MM for membranes, MP for motor-pump assemblies, EL for electronics, MA and FA for assemblies, PF for plumbing fittings — followed by SW or FW for the seawater (SeaXchange) or fresh-water (Spot Zero) side: MM-SW0001 is the 2.5 × 40 in seawater membrane, FI-FW0013 the Spot Zero pre-filter. The older numbers are nine digits beginning 2524, and the manuals still use them. Our product pages carry both, and the search box on the site finds either.
Changing a membrane: what the job involves
Spot Zero publishes a step-by-step membrane replacement guide (PDF) for the ZTC II, XTC II and XZ II, and the short version is this. Shut the system down and expect water in the bilge — have a bucket ready. Fresh-water vessels are closed with retaining plates on two M6 bolts (5 mm Allen key); slide the clips in, pull the end cap, draw the old element out by the body (never the white permeate tube). Seawater vessels add the 3/8 in quick-connect fittings and stainless tubing on the end caps. Lubricate the new element’s brine seal with a food-grade compound, push it in brine-seal last, fit new O-rings to the end cap, reassemble, and flush for at least 30 minutes with everything to waste, because new membranes ship in preservative. If you would rather we did it, we support service with your yard or engineer.
Storing a watermaker in Thailand
Boats here are laid up for the wet season more often than for winter, and a membrane left wet and warm for three months grows things. The rule is simple: if the system can be run, run it and flush it for five minutes once a month. If it cannot, pickle it: mix the storage solution with the system’s own product water, circulate it through the membrane vessels with a low-pressure chemical pump (not the system’s own pump, and never above 30 psi or 44 °C), plug the ports, and renew the solution every three months. When the boat goes back in: new pre-filter, 30-minute flush to waste, then normal running.
How we supply watermaker parts in Thailand
- Everything by part number. All 225 current Spot Zero and SeaXchange service parts are in the parts section, grouped as filters, membranes and chemicals, pumps and motors, electronics, valves and fittings, and hardware.
- At US list price. We list Spot Zero’s own prices; you are not paying a Thailand premium for the same part.
- Ordered from here, lead time confirmed first. Parts are special-ordered from the factory and come by courier; we tell you the dispatch date before you pay. Keep a season’s pre-filters and a storage bottle aboard and the lead time never matters.
- Delivered anywhere in Thailand. Free to Trang, Krabi and Phuket, free nationwide over US$250; Pattaya, Samui, Satun and the rest by courier at cost.
- Identified from a photo. Serial number plus a photo of the part by LINE @drakeco or WhatsApp, in English or Thai, and we tell you what it is and what it costs.
Frequently asked questions
How often should watermaker membranes be replaced?
Seawater membranes are replaced on condition, not on a calendar: when product-water TDS climbs and flow falls and a chemical clean does not bring them back. With a fresh-water flush after every run and correct storage during lay-ups they last for years. Fresh-water purifier membranes have hour-based intervals — Spot Zero gives 500 hours for the Mobile Pro Mini and 1,000 hours or 100,000 gallons for the 4041 element — or earlier if the product water is no longer at least 85 % cleaner than the feed.
What size membrane does my watermaker take?
Yacht watermakers use standard element sizes: 2.5 × 40 in (2540) in long pressure vessels and 2.5 × 21 in (2521) in short ones; Spot Zero purifiers use 4 × 40 in (4040/4041) and 4 × 21 in (4021) fresh-water elements. The vessel length and the system’s rated capacity tell you the size and the count. Send us the model and serial number and we confirm before you order.
How do I pickle or store a watermaker?
If the system will not be run for more than a month, the membranes are preserved with a membrane storage (pickling) solution circulated through the vessels with a low-pressure chemical pump, then the ports are plugged and the solution is renewed every three months. If the boat is stored somewhere it can be run, a five-minute fresh-water flush once a month does the same job. Recommissioning is a new pre-filter and a 30-minute flush to waste.
Can I buy watermaker parts in Thailand?
Yes. Drake Marine lists every current Spot Zero and SeaXchange service part — 225 of them — by part number at Spot Zero’s US list price, orders them from the factory with the lead time confirmed before you pay, and delivers anywhere in Thailand (free to Trang, Krabi and Phuket, free nationwide on orders over US$250).
What is the difference between a watermaker pre-filter and a water purifier pre-filter?
A seawater pre-filter is a mechanical sediment filter — typically 25 micron then 5 micron — that protects the high-pressure pump and membranes from silt and growth. A purifier pre-filter also carries activated carbon and other media, because it has to remove the chlorine and chloramine in dock water that would otherwise destroy the membrane. They are not interchangeable.
Why has my watermaker’s output dropped?
In order of likelihood: a blocked pre-filter (check the pressure drop), cold or very salty feed water (output is rated at a standard temperature and salinity), a membrane that needs a chemical clean, a worn high-pressure pump, or a membrane at the end of its life. The system’s own readings — feed pressure, product flow and product TDS — usually point at the cause.
Keep the water coming
Pre-filters, membranes, flush cartridges, cleaner and storage solution — order the season’s set in one go and it is on the shelf when the system asks for it.
Watermaker parts by part numberSize a new watermakerLINE @drakeco
