iW Solar builds the SD-S and SD-G non-pressure solar water heaters in Taian City, Shandong Province, from 10 to 30 vacuum tubes and 80 L to 230 L net capacity. Open-vented thermosiphon design, SUS304-2B inner tank and 55 mm polyurethane insulation — B2B manufacturing and OEM & ODM for importers and distributors since 2013.
A non-pressure solar water heater — also called non-pressurised or low-pressure — is an open system. The storage tank is vented to the atmosphere, water is heated directly inside the evacuated tubes and the tank, and hot water reaches the tap by gravity. There is no pump, no pressure vessel and no heat exchanger, which is exactly why it delivers the lowest cost per litre of hot water of any solar water heater type.
iW Solar manufactures the SD-S and SD-G series from 10 to 30 vacuum tubes, covering 80 L to 230 L net capacity. It is the workhorse of household solar water heating across Africa, the Middle East, South and Southeast Asia, Latin America and island markets — regions where simplicity, price and reliability decide the sale.
The system circulates water on its own. Cold water is denser than hot water, so inside every evacuated tube a natural cycle starts and keeps running all day — no pump, and no electricity spent on circulation.
Seven standard configurations. The SD-S and SD-G versions share the same tank and tube specification and differ in tank finish and frame build.
| Model | Vacuum tubes | Net tank capacity | Gross capacity |
|---|---|---|---|
| SD-S-10 / SD-G-10 | 10 pcs | 80 L | 105 L |
| SD-S-15 / SD-G-15 | 15 pcs | 120 L | 155 L |
| SD-S-18 / SD-G-18 | 18 pcs | 140 L | 185 L |
| SD-S-20 / SD-G-20 | 20 pcs | 155 L | 205 L |
| SD-S-24 / SD-G-24 | 24 pcs | 185 L | 245 L |
| SD-S-25 / SD-G-25 | 25 pcs | 195 L | 255 L |
| SD-S-30 / SD-G-30 | 30 pcs | 230 L | 305 L |
| Item | Specification |
|---|---|
| Inner / outer tank diameter | Φ360 mm / Φ470 mm |
| Inner tank material | SUS304-2B (SUS316L optional) |
| Outer tank material | Stainless steel plate / colour steel plate |
| Insulation | Polyurethane, 55 mm high-pressure foaming |
| Vacuum tube | Φ58 × 1,800 mm, high borosilicate glass 3.3 |
| Frame | Stainless steel / galvanised steel, 2 feet or 3 feet |
| Mounting angle | 45° |
| Backup heating | Electric heater with intelligent controller |
| Water quality | Suited to hard and poor-quality water when the SUS316L tank is selected |
| Quality control | Full-process inspection; tank pressure test; AQL 2.5 packing check; third-party inspection welcome |
Choose a non-pressure system when your customers want the lowest purchase price, have weak or no mains pressure, and are happy with gravity-fed hot water. It has fewer parts to fail, installs in a few hours, and is the easiest product to sell on payback time.
Choose a pressurised or split system when your customers expect strong, mains-pressure showers or want the tank hidden indoors. Those systems cost more but fit premium housing. iW Solar manufactures both — we will tell you honestly which one suits your market instead of pushing you into one range.
Want the non-pressure concept built around a flat plate collector instead of tubes? That exists too: the iW-FT non-pressurised flat plate solar water heater (150–300 L) pairs with the collector on our flat plate solar collector page. For a side-by-side view of the main system types, see the different types of solar water heaters.
iW Solar is a B2B manufacturer, not a retail shop, so the heater is built around your business:
See the full solar water heater product range for the pressurised, split and combi options that complete a catalogue.
The tank is open and vented, so it never holds line pressure. Hot water flows to the tap by gravity, which is why the system is simpler and cheaper than a pressurised one — and why it is unaffected by weak or intermittent mains pressure.
Not directly. A non-pressure system delivers gravity flow only. If a strong pressure shower is expected, either add a booster pump or move to a pressurised or split system — we manufacture both and will recommend the right one for your market.
An electric heater inside the tank, controlled by the intelligent controller, provides backup heating so the household always has hot water. It can also be combined with a gas or boiler backup.
It is the best-selling type across Africa, the Middle East, South and Southeast Asia, Latin America and island markets — anywhere with strong sunlight, price-sensitive buyers and no hard freezing winters.
Yes. Logo printing on the outer tank, custom cartons and manual branding are standard OEM services, and the colour-steel outer tank can be finished to your market preference.
MOQ starts from 1 set for market testing. Production takes 18–25 working days after order confirmation, and we reply to every enquiry within 12 hours.
Tell us your target market, target retail price and estimated annual quantity. Our engineers will come back with the right tube and tank configuration, and a price, within 12 hours.
Request a quotation See all solar water heater productsCompetitive pricing, exceptional quality — get a factory quote within 12 hours.
If you are looking for an experienced and reliable factory for your OEM custom solar water heaters and bespoke solar equipment in China, iWSOLAR is your best choice. We offer the most reasonable price with the finest quality to support your business.