Membrane

Replacement membranes for expansion vessels and pressure tanks: EPDM and butyl, 2 liters to 5,000 liters, with 80 mm throat diameter, in various capacities.

Products (9)

24 L Expansion Vessel Membrane, Domestically Made, Throat Diameter 80 mm – $4.96
Expansion Vessel Membrane, 24 L, Italian Made, Bladder Type, Throat Diameter 80 mm – $5.46
Forza FRZ0089 EPDM Expansion Vessel Membrane, 24 L – $7.00
Hidrotank 80-100 L Diaphragm, Italian Made, 80 mm Throat Diameter, Dual Chamber, Closed Top – $26.85
Kentaş 5000 Butyl Pressure Tank Diaphragm, 5,000 L – Request a quote
Kentaş EPDM Pressure Tank Diaphragm, 2/3 L – Request a quote
Membrane, 150/200 L, Domestically Manufactured, Neck Diameter 80 mm, Dual-Volume, Top-Perforated – $49.12
Membrane for 80-100 L Tanks, Italian Made, 80 mm Throat Diameter, Dual Chamber, Top Hole – $30.09
Nortek EPDM Pressure Tank Membrane, 24 L, 80/110 mm – $6.71

Brands: Forza · Hidrotank · Kentaş · Nortek

What does a membrane do?

In expansion vessels and pressure tanks with a replaceable membrane, water contacts a flexible bag (membrane) inside the tank rather than the metal body. Pressurized air is held between the outside of the membrane and the tank body. When the pump runs, the membrane fills with water and expands; when a tap is opened, the air pressure compresses the membrane and pushes the water into the system. When the membrane ruptures, water reaches the body, the tank loses its function, and the pump begins to cycle very frequently.

Signs of membrane failure

The pump starts immediately every time a tap is opened
Water instead of air comes from the tank's valve stem
The tank is completely full of water and feels heavy
Pressure drops and rises very rapidly

When these signs appear, first check the tank air pressure; if water comes from the valve stem, the membrane has ruptured.

Choosing the correct membrane

The replacement membrane must match the tank's capacity, neck (mouth) diameter, and intended application. Many models in the category have an 80 mm neck diameter; check your tank's flange size. EPDM and butyl are the most commonly used membrane materials; for drinking water tanks, a membrane approved for potable water should be chosen. Membranes described as dual-capacity are manufactured to fit the two stated tank capacities. For large-capacity tanks, whether the membrane is top-supported should also be taken into account.

How is the replacement carried out?

Turn off the pump, release the system pressure, and deflate the tank air via the valve stem. Remove the flange bolts, take out the old membrane, and clean the inside of the tank. Fit the new membrane and close the flange with even tightening. Finally, set the tank air pressure to the system values with the water side empty, then start the system.

Frequently asked questions

Should the membrane be replaced, or the whole tank?

For tanks with a replaceable membrane whose body is in good condition, replacing only the membrane is an economical solution.

What is the service life of a membrane?

It depends on usage intensity, water quality, and whether the air pressure is checked regularly.

Can the membrane be replaced in a fixed-membrane tank?

In fixed-membrane tanks, replacing the membrane separately is generally not possible.

How do I determine the correct membrane size?

Measure the tank capacity and flange diameter and compare them with the product specifications.

What should the tank pressure be after fitting a new membrane?

It should be slightly below the pump cut-in pressure.

What if I want to replace the entire tank?

For new tanks, you can browse the expansion vessels category.