Three-Way Valve Saunier Duval Isofast, Isomax and Other Ranges - Ref. S1025500
The Saunier Duval Isofast, Isomax, and other ranges' 3-way valve - Ref. S1025500, is a device that switches water between the heating circuit and the domestic hot water circuit. When it fails, you may notice that there is hot water but no heating, or both circuits may mix, which can trigger the fault code F.20: safety disconnection due to temperature limiter. This valve is compatible with boilers such as F 35 E-A, F 30 E-A, C 35 E-A, among others from the Isofast, Isomax, Isotwin, and Themafast ranges. It should be replaced when the mentioned symptoms occur or when a malfunction of the heating or hot water is detected.
VAT included
Consult via WhatsAppSaunier Duval boilers compatible with reference S1025500
3-way valve with reference S1025500. 18 verified compatibilities: F 35 E-A and F 30 E-A.
Proven compatibility
| Boiler model | Family | Verification |
|---|---|---|
| Saunier Duval F 35 E-A | Isofast | Contrasted |
| Saunier Duval F 30 E-A | Isofast | Contrasted |
| Saunier Duval C 35 E-A | Isofast | Contrasted |
| Saunier Duval F 35 E H-MOD | Isofast | Contrasted |
| Saunier Duval F 30 E H-MOD | Isofast | Contrasted |
| Saunier Duval Condens F 30 E | Isofast | Contrasted |
| Saunier Duval Condens F 35 E | Isofast | Contrasted |
| Saunier Duval F 35 E | Isomax | Contrasted |
| Saunier Duval F 35 H-MOD | Isomax | Contrasted |
| Saunier Duval Condens F 35 E | Isomax | Contrasted |
| Saunier Duval F 30 H-MOD | Isotwin | Contrasted |
| Saunier Duval Condens F 30 E | Isotwin | Contrasted |
| Saunier Duval F 25 E | Themafast | Contrasted |
| Saunier Duval F 30 E | Themafast | Contrasted |
| Saunier Duval C 25 E | Themafast | Contrasted |
| Saunier Duval C 30 E | Themafast | Contrasted |
| Saunier Duval Condens F 25 | Themafast | Contrasted |
| Saunier Duval Condens F 30 | Themafast | Contrasted |
Can't see your model or have questions? The printed reference takes precedence. How to check it · Send us a photo via WhatsApp.
How to check if ref. S1025500 is the part for your boiler
What determines it is not the boiler model, but the reference printed on the part you already have installed.
- Find the reference printed on the installed part and check whether it matches the catalogue reference S1025500. If it is not visible, do not identify the part from its shape alone.
- Check the full boiler model on its data plate and look for it in the model associations on this page.
- Compare the connections and physical body with the original part before installation.
- If anything is unclear, send us a photo of the marking via WhatsApp before placing your order.
Symptoms and faults that the S1025500 three-way valve resolves.
The 3-way valve diverts water between heating and domestic hot water. These are the typical symptoms and what to do:
Common symptoms and faults
- 01
The tap water comes out lukewarm or cold while the radiators are working well, or vice versa.
Cause: The valve is not directing the water correctly to the corresponding circuit.
Measure the temperature in each circuit separately before deciding that the valve is the culprit.
- 02
Do you see moisture or dripping on the body of the gas valve, even though the rest of the installation is dry?
Cause: The internal seals of the gas valve have lost their sealing capacity over time.
Dry the area and turn on the boiler to identify the exact point of the leak before replacing the part.
- 03
The boiler takes a long time to switch service or resists doing so.
Cause: The switching mechanism is stuck due to dirt, limescale, or wear.
Bleed the circuit and check for any limescale residue in the area before replacing the gas valve.
Fault codes from Saunier Duval that this spare part resolves.
| Code | Fault | Diagnosis and solution |
|---|---|---|
| F.20 | Safety shutdown: temperature limiter. | If the 3-way valve (priority valve) is blocked or disconnected, the primary flow does not switch correctly and the generator overheats, triggering the F.20; to verify, force the test/diagnosis that moves the valve from the service menu and check the power supply/wiring and ensure the shaft/motor are not seized. |
These symptoms can have more than one cause. If your boiler displays a fault code, send it to us via WhatsApp along with a photo of the labeling, and we'll tell you if this is the part.
Data sheet for the Saunier Duval 3-way valve S1025500.
- Catalogue reference
- S1025500
- Brand
- Saunier Duval
- Type of part
- 3-way valves
- Units in stock
- 1 unit
- Status
- Refurbished
- Warranty
- 1 year
- Shipping
- 1-2 business days
- Return
- 14 days
Data read on the part and in the manufacturer's documentation
What we have not been able to verify does not appear here.
- material
- PA66
Manuals and technical documentation
Official documentation of the boiler, useful for locating the part and cross-referencing the fault codes.
- Saunier Duval F 25 E Manual (PDF)Document © Saunier Duval, provided as a technical reference.
Frequently asked questions about the 3-way valve S1025500
What is the reference for the Saunier Duval 3-way valve that I need to order?
For which ranges of Saunier Duval boilers is this 3-way valve compatible?
How many boiler models are compatible with this gas valve?
What symptoms indicate that I should replace this gas valve in my boiler?
What fault code is documented for this gas valve?
Spare parts related to Saunier Duval Isofast
