Saunier Duval Isofast 3-Way Valve Ref. S1025500
The Saunier Duval Isofast 3-way valve is a component that directs the flow of water between the heating circuit and the domestic hot water circuit. If it fails, you may notice that there is hot water but no heating, or vice versa, or that both circuits are mixing. This valve is compatible with several models, including the F 35 E-A, F 30 E-A, C 35 E-A, among others. It is advisable to replace it when you experience these operational issues, especially if the fault code F.20 appears: Safety disconnection: temperature limiter.
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
There is no hot water coming from the tap, but the heating works fine.
Cause: The valve is stuck in the heating position and does not divert water to the tap.
Open a hot water tap and listen to see if the gas valve motor tries to move; if it doesn't, check that it is receiving power.
- 02
There is hot water at the tap, but when the heating is turned on, the radiators do not heat up.
Cause: The valve remains in the hot water position and does not allow water to circulate through the heating system.
Check if the circulation pump works when the heating is activated; if it does and the radiators remain cold, the valve could be the issue.
- 03
A thump or rattling sound is heard just when the boiler switches from one mode to another.
Cause: The internal shutter does not move correctly, usually due to scale or wear, and hits at the end of its travel.
Check if the knock occurs only when switching modes and not at any other time during the ignition cycle.
- 04
Water is appearing at the base of the boiler, near the body of the 3-way valve.
Cause: The internal O-rings lose their sealing capability over time, and water begins to leak through the body.
Dry the area, let the boiler run for a while, and locate the exact point of the leak before assuming it is the gas valve and not a nearby fitting.
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
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
Is this 3-way valve reference S1025500 compatible with the Isofast range from Saunier Duval?
Does the 3-way valve S1025500 work for the Isomax range from Saunier Duval?
Can I use the S1025500 valve in a boiler from the Isotwin range?
How many models are compatible with the Saunier Duval S1025500 three-way valve?
What fault code is documented for this gas valve?
Does the reference V3VIF35EHMOD correspond to the 3-way valve S1025500?
Spare parts related to Saunier Duval Isofast
