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Zilmet Hydro-Pro 35 Litre Potable Expansion Vessel 1 inch BSP Floor Mounted
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Zilmet Hydro-Pro 35 Litre Potable Expansion Vessel 1 inch BSP Floor Mounted

Zilmet Hydro-Pro 35 Litre Potable Expansion Vessel 1 inch BSP Floor Mounted

The Zilmet Hydro-Pro 35 L (MPN: 11A0003535) is a floor-standing potable water expansion vessel with 1" BSP connections, designed for domestic and light-commercial hot water systems including unvented cylinders, pressurised water heaters and pump systems. It features a fixed butyl membrane approved for contact with drinking water, an internal epoxy coating to prevent corrosion, and an exclusive MIG-welded carbon steel shell that eliminates sharp internal edges which could otherwise damage the membrane. Rated to 10 bar working pressure and an operating temperature range of −10 °C to +99 °C, with a pre-charge of 2.0 bar. Approved to PED 2014/68/EU, WRAS, ACS, IAPMO and NSF standards. The floor-standing 1" BSP configuration (11A0003535) is suitable for high-demand installations where a wall-hung vessel would be undersized.

35 L
Volume
10 bar
Max working pressure
99 °C
Max temperature
2.0 bar
Pre-charge pressure
WRAS
Approved
Potable water rated: The Hydro-Pro uses a butyl membrane approved for drinking water contact. It must not be substituted with a heating expansion vessel, whose membrane is not food-safe. The two vessel types are not interchangeable.
Sizing note: At 35 litres, the Hydro-Pro is suited to larger unvented cylinders (typically 210–300 L) or installations with higher incoming water pressure. Always size the vessel using the cylinder manufacturer's sizing table, based on cylinder volume, incoming pressure and T&P valve set pressure.
Key Features
Fixed Butyl Membrane — Potable Approved

The fixed butyl membrane is specifically formulated and approved for potable (drinking) water contact. It is seamless and non-stretching, with no bubbles or internal corners that could trap stagnant water and promote bacterial growth. The membrane's compact dome shape keeps it in permanent intimate contact with the vessel wall, maximising effective volume utilisation.

MIG-Welded Carbon Steel Shell

Zilmet uses an exclusive MIG welding process that eliminates sharp internal edges and rough weld profiles. This prevents abrasion damage to the butyl membrane, which is the primary cause of premature membrane failure in lower-quality vessels. The smooth internal profile also makes the vessel easier to clean during servicing.

Internal Epoxy Coating

The interior of the carbon steel shell is protected by an exclusive internal epoxy coating, preventing the steel from corroding in the presence of moisture. The exterior carries an epoxy-polyester powder-coat finish for corrosion resistance in damp plant rooms. Together these coatings extend service life significantly compared to uncoated or single-coat vessels.

Floor-Standing — 1" BSP Connection

The 11A0003535 variant is floor-standing with a 1" BSP connection. The floor-standing design is ideal where wall space is limited or where the vessel weight (filled) makes wall hanging impractical. The 1" BSP connection suits direct connection to the system pipework without the need for a reducer, simplifying installation on larger cylinder systems.

International Certifications

The Hydro-Pro 35 carries PED 2014/68/EU, WRAS, ACS, IAPMO and NSF approvals — confirming compliance with European and international pressure equipment and potable water contact regulations. WRAS approval is particularly significant for UK installations, confirming suitability for connection to the mains water supply.

Protected Pre-Charge Valve

The air pre-charge valve is protected by a tamper-resistant cap to prevent accidental interference and contamination during installation and service. The pre-charge of 2.0 bar should be verified at commissioning and checked at each service with the water side de-pressurised.

Technical Specifications
Parameter Value
MPN / Part number 11A0003535
Volume 35 litres
Max working pressure 10 bar
Operating temperature range −10 °C to +99 °C
Pre-charge pressure 2.0 bar
Connection size 1" BSP
Mounting type Floor standing
Application Potable water (DHW unvented systems, pressurised water heaters)
Membrane type Fixed butyl — potable water approved, non-replaceable
Shell material Carbon steel, MIG welded
Internal coating Exclusive epoxy coating
External coating Epoxy-polyester powder coat
Approvals PED 2014/68/EU, WRAS, ACS, IAPMO, NSF
Manufacturer Zilmet SpA, Limena, Italy
Frequently Asked Questions
Why choose the Zilmet Hydro-Pro over a standard expansion vessel?
The Hydro-Pro is a premium potable-rated vessel with several engineering advantages over budget alternatives: the MIG-welded smooth interior prevents membrane abrasion; the internal epoxy coating prevents corrosion that can contaminate water; and the seamless butyl membrane geometry prevents stagnant water pockets. WRAS approval confirms it meets UK Water Regulations for connection to the mains supply — not all vessels on the market carry this approval.
Can this vessel be used on a central heating circuit?
No. The Hydro-Pro is designed exclusively for potable (drinking water) circuits. Central heating systems require a heating expansion vessel (such as the Zilmet Cal-Pro range) with an SBR rubber diaphragm suitable for glycol solutions and heating water. Using a potable vessel on a heating circuit may cause premature membrane failure.
Where should the Hydro-Pro 35 be installed?
The vessel should be connected to the cold water inlet pipework downstream of the PRV and upstream of the non-return valve — or in the dedicated expansion vessel port on the cylinder's inlet control group. Floor-standing models should be positioned upright with the connection at the top (as supplied). Ensure the connection point is accessible for annual pre-charge pressure checks.
How do I check and adjust the pre-charge pressure?
At each annual service: isolate the vessel from the system and depressurise the water side completely before checking. Use a standard tyre-type pressure gauge on the air valve (after removing the protective cap). The correct pre-charge for the Hydro-Pro 35 is 2.0 bar. Top up with dry nitrogen or clean, dry compressed air if the pressure has dropped. Never check pre-charge with the water side pressurised — the reading will be inaccurate.
$68.97

Original: $197.05

-65%
Zilmet Hydro-Pro 35 Litre Potable Expansion Vessel 1 inch BSP Floor Mounted—

$197.05

$68.97

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Zilmet Hydro-Pro 35 Litre Potable Expansion Vessel 1 inch BSP Floor Mounted - Image 2

Zilmet Hydro-Pro 35 Litre Potable Expansion Vessel 1 inch BSP Floor Mounted

The Zilmet Hydro-Pro 35 L (MPN: 11A0003535) is a floor-standing potable water expansion vessel with 1" BSP connections, designed for domestic and light-commercial hot water systems including unvented cylinders, pressurised water heaters and pump systems. It features a fixed butyl membrane approved for contact with drinking water, an internal epoxy coating to prevent corrosion, and an exclusive MIG-welded carbon steel shell that eliminates sharp internal edges which could otherwise damage the membrane. Rated to 10 bar working pressure and an operating temperature range of −10 °C to +99 °C, with a pre-charge of 2.0 bar. Approved to PED 2014/68/EU, WRAS, ACS, IAPMO and NSF standards. The floor-standing 1" BSP configuration (11A0003535) is suitable for high-demand installations where a wall-hung vessel would be undersized.

35 L
Volume
10 bar
Max working pressure
99 °C
Max temperature
2.0 bar
Pre-charge pressure
WRAS
Approved
Potable water rated: The Hydro-Pro uses a butyl membrane approved for drinking water contact. It must not be substituted with a heating expansion vessel, whose membrane is not food-safe. The two vessel types are not interchangeable.
Sizing note: At 35 litres, the Hydro-Pro is suited to larger unvented cylinders (typically 210–300 L) or installations with higher incoming water pressure. Always size the vessel using the cylinder manufacturer's sizing table, based on cylinder volume, incoming pressure and T&P valve set pressure.
Key Features
Fixed Butyl Membrane — Potable Approved

The fixed butyl membrane is specifically formulated and approved for potable (drinking) water contact. It is seamless and non-stretching, with no bubbles or internal corners that could trap stagnant water and promote bacterial growth. The membrane's compact dome shape keeps it in permanent intimate contact with the vessel wall, maximising effective volume utilisation.

MIG-Welded Carbon Steel Shell

Zilmet uses an exclusive MIG welding process that eliminates sharp internal edges and rough weld profiles. This prevents abrasion damage to the butyl membrane, which is the primary cause of premature membrane failure in lower-quality vessels. The smooth internal profile also makes the vessel easier to clean during servicing.

Internal Epoxy Coating

The interior of the carbon steel shell is protected by an exclusive internal epoxy coating, preventing the steel from corroding in the presence of moisture. The exterior carries an epoxy-polyester powder-coat finish for corrosion resistance in damp plant rooms. Together these coatings extend service life significantly compared to uncoated or single-coat vessels.

Floor-Standing — 1" BSP Connection

The 11A0003535 variant is floor-standing with a 1" BSP connection. The floor-standing design is ideal where wall space is limited or where the vessel weight (filled) makes wall hanging impractical. The 1" BSP connection suits direct connection to the system pipework without the need for a reducer, simplifying installation on larger cylinder systems.

International Certifications

The Hydro-Pro 35 carries PED 2014/68/EU, WRAS, ACS, IAPMO and NSF approvals — confirming compliance with European and international pressure equipment and potable water contact regulations. WRAS approval is particularly significant for UK installations, confirming suitability for connection to the mains water supply.

Protected Pre-Charge Valve

The air pre-charge valve is protected by a tamper-resistant cap to prevent accidental interference and contamination during installation and service. The pre-charge of 2.0 bar should be verified at commissioning and checked at each service with the water side de-pressurised.

Technical Specifications
Parameter Value
MPN / Part number 11A0003535
Volume 35 litres
Max working pressure 10 bar
Operating temperature range −10 °C to +99 °C
Pre-charge pressure 2.0 bar
Connection size 1" BSP
Mounting type Floor standing
Application Potable water (DHW unvented systems, pressurised water heaters)
Membrane type Fixed butyl — potable water approved, non-replaceable
Shell material Carbon steel, MIG welded
Internal coating Exclusive epoxy coating
External coating Epoxy-polyester powder coat
Approvals PED 2014/68/EU, WRAS, ACS, IAPMO, NSF
Manufacturer Zilmet SpA, Limena, Italy
Frequently Asked Questions
Why choose the Zilmet Hydro-Pro over a standard expansion vessel?
The Hydro-Pro is a premium potable-rated vessel with several engineering advantages over budget alternatives: the MIG-welded smooth interior prevents membrane abrasion; the internal epoxy coating prevents corrosion that can contaminate water; and the seamless butyl membrane geometry prevents stagnant water pockets. WRAS approval confirms it meets UK Water Regulations for connection to the mains supply — not all vessels on the market carry this approval.
Can this vessel be used on a central heating circuit?
No. The Hydro-Pro is designed exclusively for potable (drinking water) circuits. Central heating systems require a heating expansion vessel (such as the Zilmet Cal-Pro range) with an SBR rubber diaphragm suitable for glycol solutions and heating water. Using a potable vessel on a heating circuit may cause premature membrane failure.
Where should the Hydro-Pro 35 be installed?
The vessel should be connected to the cold water inlet pipework downstream of the PRV and upstream of the non-return valve — or in the dedicated expansion vessel port on the cylinder's inlet control group. Floor-standing models should be positioned upright with the connection at the top (as supplied). Ensure the connection point is accessible for annual pre-charge pressure checks.
How do I check and adjust the pre-charge pressure?
At each annual service: isolate the vessel from the system and depressurise the water side completely before checking. Use a standard tyre-type pressure gauge on the air valve (after removing the protective cap). The correct pre-charge for the Hydro-Pro 35 is 2.0 bar. Top up with dry nitrogen or clean, dry compressed air if the pressure has dropped. Never check pre-charge with the water side pressurised — the reading will be inaccurate.

Product Information

Shipping & Returns

Description

The Zilmet Hydro-Pro 35 L (MPN: 11A0003535) is a floor-standing potable water expansion vessel with 1" BSP connections, designed for domestic and light-commercial hot water systems including unvented cylinders, pressurised water heaters and pump systems. It features a fixed butyl membrane approved for contact with drinking water, an internal epoxy coating to prevent corrosion, and an exclusive MIG-welded carbon steel shell that eliminates sharp internal edges which could otherwise damage the membrane. Rated to 10 bar working pressure and an operating temperature range of −10 °C to +99 °C, with a pre-charge of 2.0 bar. Approved to PED 2014/68/EU, WRAS, ACS, IAPMO and NSF standards. The floor-standing 1" BSP configuration (11A0003535) is suitable for high-demand installations where a wall-hung vessel would be undersized.

35 L
Volume
10 bar
Max working pressure
99 °C
Max temperature
2.0 bar
Pre-charge pressure
WRAS
Approved
Potable water rated: The Hydro-Pro uses a butyl membrane approved for drinking water contact. It must not be substituted with a heating expansion vessel, whose membrane is not food-safe. The two vessel types are not interchangeable.
Sizing note: At 35 litres, the Hydro-Pro is suited to larger unvented cylinders (typically 210–300 L) or installations with higher incoming water pressure. Always size the vessel using the cylinder manufacturer's sizing table, based on cylinder volume, incoming pressure and T&P valve set pressure.
Key Features
Fixed Butyl Membrane — Potable Approved

The fixed butyl membrane is specifically formulated and approved for potable (drinking) water contact. It is seamless and non-stretching, with no bubbles or internal corners that could trap stagnant water and promote bacterial growth. The membrane's compact dome shape keeps it in permanent intimate contact with the vessel wall, maximising effective volume utilisation.

MIG-Welded Carbon Steel Shell

Zilmet uses an exclusive MIG welding process that eliminates sharp internal edges and rough weld profiles. This prevents abrasion damage to the butyl membrane, which is the primary cause of premature membrane failure in lower-quality vessels. The smooth internal profile also makes the vessel easier to clean during servicing.

Internal Epoxy Coating

The interior of the carbon steel shell is protected by an exclusive internal epoxy coating, preventing the steel from corroding in the presence of moisture. The exterior carries an epoxy-polyester powder-coat finish for corrosion resistance in damp plant rooms. Together these coatings extend service life significantly compared to uncoated or single-coat vessels.

Floor-Standing — 1" BSP Connection

The 11A0003535 variant is floor-standing with a 1" BSP connection. The floor-standing design is ideal where wall space is limited or where the vessel weight (filled) makes wall hanging impractical. The 1" BSP connection suits direct connection to the system pipework without the need for a reducer, simplifying installation on larger cylinder systems.

International Certifications

The Hydro-Pro 35 carries PED 2014/68/EU, WRAS, ACS, IAPMO and NSF approvals — confirming compliance with European and international pressure equipment and potable water contact regulations. WRAS approval is particularly significant for UK installations, confirming suitability for connection to the mains water supply.

Protected Pre-Charge Valve

The air pre-charge valve is protected by a tamper-resistant cap to prevent accidental interference and contamination during installation and service. The pre-charge of 2.0 bar should be verified at commissioning and checked at each service with the water side de-pressurised.

Technical Specifications
Parameter Value
MPN / Part number 11A0003535
Volume 35 litres
Max working pressure 10 bar
Operating temperature range −10 °C to +99 °C
Pre-charge pressure 2.0 bar
Connection size 1" BSP
Mounting type Floor standing
Application Potable water (DHW unvented systems, pressurised water heaters)
Membrane type Fixed butyl — potable water approved, non-replaceable
Shell material Carbon steel, MIG welded
Internal coating Exclusive epoxy coating
External coating Epoxy-polyester powder coat
Approvals PED 2014/68/EU, WRAS, ACS, IAPMO, NSF
Manufacturer Zilmet SpA, Limena, Italy
Frequently Asked Questions
Why choose the Zilmet Hydro-Pro over a standard expansion vessel?
The Hydro-Pro is a premium potable-rated vessel with several engineering advantages over budget alternatives: the MIG-welded smooth interior prevents membrane abrasion; the internal epoxy coating prevents corrosion that can contaminate water; and the seamless butyl membrane geometry prevents stagnant water pockets. WRAS approval confirms it meets UK Water Regulations for connection to the mains supply — not all vessels on the market carry this approval.
Can this vessel be used on a central heating circuit?
No. The Hydro-Pro is designed exclusively for potable (drinking water) circuits. Central heating systems require a heating expansion vessel (such as the Zilmet Cal-Pro range) with an SBR rubber diaphragm suitable for glycol solutions and heating water. Using a potable vessel on a heating circuit may cause premature membrane failure.
Where should the Hydro-Pro 35 be installed?
The vessel should be connected to the cold water inlet pipework downstream of the PRV and upstream of the non-return valve — or in the dedicated expansion vessel port on the cylinder's inlet control group. Floor-standing models should be positioned upright with the connection at the top (as supplied). Ensure the connection point is accessible for annual pre-charge pressure checks.
How do I check and adjust the pre-charge pressure?
At each annual service: isolate the vessel from the system and depressurise the water side completely before checking. Use a standard tyre-type pressure gauge on the air valve (after removing the protective cap). The correct pre-charge for the Hydro-Pro 35 is 2.0 bar. Top up with dry nitrogen or clean, dry compressed air if the pressure has dropped. Never check pre-charge with the water side pressurised — the reading will be inaccurate.