3-Way Valve Saunier Duval Isofast F 30 E Ref. S1025500
The 3-way valve Saunier Duval Isofast F 30 E Ref. S1025500 is a component that regulates the flow of 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 vice versa, or that both circuits are mixing. This valve is compatible with boilers from the Isofast, Isomax, Isotwin, and Themafast ranges, such as models F 30 E-A, F 35 E, and F 25 E, among others. It should be replaced when it shows signs of malfunction or faults such as F.20, which indicates a safety disconnection due to a 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
You turn on the hot water tap and it takes a long time to come out warm, or it doesn't heat up at all.
Cause: The motor has not moved the valve to the domestic hot water position and the water continues to be diverted to the heating circuit.
Open a hot water tap and listen for the valve motor to click and turn; if it doesn't move, check the power supply to the motor before checking the valve itself.
- 02
The tap water comes out neither completely cold nor hot, as if it is mixing with the heating water.
Cause: The internal shutter does not close properly on one of the passages and allows water to flow from both circuits at the same time.
Check the temperature at the tap with the boiler only in heating mode, without requesting domestic hot water; if any hot water comes out, there is internal leakage in the gas valve.
- 03
There is a drip or puddle of water in the area of the gas valve, either from the body or where the motor enters.
Cause: The internal seals wear out with use and water starts to leak from where it shouldn't.
Dry the area well and check again after a heating cycle and another for domestic hot water, to locate whether the leak is coming from the body of the gas valve or from a nearby connection.
- 04
The boiler can't seem to decide between heating and domestic hot water: it goes back and forth, or it gets stuck halfway.
Cause: The motor does not complete the travel to the limit, and the control board does not receive the position confirmation.
Observe a complete cycle of domestic hot water startup: if the motor starts to turn and stops before reaching the end, it points to the valve or the motor, not to the PCB.
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.
- Component code
- S1025500
- CE marking
- Yes, symbol printed on the label
- Country/area of manufacture
- Made in EU (legend printed on the label)
Frequently asked questions about the 3-way valve S1025500
What fault indicates that the 3-way valve needs to be replaced in a Saunier Duval Isofast F 30 E?
Is the reference S1025500 for this gas valve confirmed on the label?
Does this valve fit an Isotwin C 30 or only the Isofast F 30 E?
Does the label on this gas valve have a CE mark?
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