Expansion Vessel for Combitek C 23 Boiler and Others - Ref. 05705800

Saunier Duval boilers compatible with reference 05705800

Expansion vessel with reference 05705800. 11 verified compatibilities: Combitek C 23 and Combitek C 23 E.

Proven compatibility

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. 05705800 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.

1. Find the reference printed on the installed part and check whether it matches the catalogue reference 05705800. If it is not visible, do not identify the part from its shape alone.
2. Check the full boiler model on its data plate and look for it in the model associations on this page.
3. Compare the connections and physical body with the original part before installation.
4. If anything is unclear, send us a photo of the marking via WhatsApp before placing your order.

Symptoms and faults that the expansion vessel 05705800 resolves.

The expansion vessel absorbs the expansion of water when heated. These are the typical symptoms and what to do:

Common symptoms and faults

• 01

  The pressure rises above normal as soon as the heating is turned on and drops again when it's turned off.

  Cause: An expansion vessel without pre-charge air allows all the water expansion to be directly translated into circuit pressure.

  Measure the air pressure in the Schrader valve of the tank with the water circuit empty: if it reads zero or very low, it has lost the precharge.

• 02

  The circuit gradually loses pressure over several days, without any visible water leak.

  Cause: If the internal membrane of the expansion vessel is cracked, the water seeps into the air chamber and disappears from the circuit without leaving a visible puddle.

  Press the air valve of the expansion vessel: if water comes out instead of just air, the diaphragm is punctured and the vessel needs to be replaced.

• 03

  You hear banging or vibration in the pipes right when the boiler starts or stops.

  Cause: The expansion vessel also absorbs the pressure surges from the pump start-up; without absorption capacity, that shock travels throughout the installation.

  Bleed the air from radiators and pump before attributing the water hammer to the expansion vessel, because trapped air causes the same noise.

• 04

  The safety valve drips intermittently, more so on colder days or when the boiler is working harder.

  Cause: The more water expansion the expansion vessel has to absorb, the sooner it becomes noticeable if it no longer has sufficient air pressure.

  Check if the dripping started right after a recent filling of the circuit, to rule out an initial excess pressure instead of an empty expansion vessel.

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 expansion vessel 05705800

Catalogue reference

05705800

Brand

Saunier Duval

Type of part

Expansion vessels

Units in stock

5 units

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 Combitek C 23 E Manual (PDF)Document © Saunier Duval, provided as a technical reference.