Does An Unvented Water Heater Need An Expansion Vessel?


The vessel is connected by pipework to the unvented cylinder, typically onto the mains cold inlet pipework, and as water in the cylinder expands it is pushed into the expansion vessel, compressing the air within the diaphragm.

When would you use an expansion vessel?

If you have a closed-water heating system in your home, such as a combi boiler, you will have an expansion vessel. Put simply, it acts as a kind of shock absorber, handling the expansion and contraction of water in your central heating system as it heats and cools.

Do you need a boiler with an unvented cylinder?

Unvented cylinders, on the other hand, are connected directly to the mains. This removes any need for a cold water tank in the loft and is why they need to be installed alongside a system boiler.

What are the advantages of an unvented cylinder?

An unvented hot water cylinder doesn’t require a feeder tank in the loft and frees up valuable space in your property. Unlike vented cylinders, the unvented cylinder doesn’t rely on gravity to function, so it can be installed almost anywhere in your home! This makes it easier to store in a place more suitable for you.

What is a system boiler with an unvented cylinder?

Unvented cylinders are commonly used as part of a system boiler installation as this enables you to take advantage of the high-pressure water supply. If you have limited space in your loft, you will be pleased to hear that unvented cylinders take up less space than vented cylinders as no feeder tank is required.

How long does an expansion vessel last?

An expansion vessel should last between 5-10 years.

What happens when expansion tank fails?

Oftenthe diaphragm dividing the two systems will fail, causing the two systems to become one. When this happens, the expansion tank turns into a “dead leg” that will eventually cause damage and premature failure to your water heater.

What pressure should my hot water expansion tank be set at?

The recommended water pressure is between 50 and 60 PSI. Thermal Expansion Tanks contain an air bladder which is pressurized with air, and expands and contracts to absorb the expanded water from the water heater. needed. Check the air pressure in the Expansion Tank using a tire gauge.

How do you drain an expansion vessel?

3 Answers

  1. Turn off the valve that auto-fills the system from your cold water line.
  2. If you have one, open a valve or bleeder on the top of your expansion tank. …
  3. Open a drain valve and drain a suitable amount of water.
  4. Close drain valve and re-open valve you closed in step 1.

Do I need an expansion tank if I have a pressure relief valve?

An expansion tank is always highly recommended if you have a ‘closed-loop system’ caused by any kind of check valve or pressure regulating valve installed on your house’s water supply line. … These are much more likely to fail prematurely when exposed to high water pressure. If you have excess pressure over 80 P.S.I.

Why do unvented cylinders explode?

It opens when the pressure inside the tank reaches extremely high levels, letting out water and lowering the pressure inside. If the valve is leaking, it means there is too much heat or pressure inside the tank. Either is dangerous as it could lead to an explosion.


Where do you put an expansion vessel on a heating system?

The Expansion Vessel must be fitted to the Return Side of the Central Heating System and in such a way that there can at no time be an obstruction between the vessel and the system.

Why does my expansion vessel lose pressure?

Pressure loss may be caused from a leak in the pressure relief valve, an issue in the expansion vessel, air in your system, or a leak in the heating pipework itself. In this article, we give you a few options that you can do on your own, before you call a licensed HVAC technician.

Why is my expansion vessel full of water?

Dripping water is one sign that a valve may be blocked. This can occur as a result of mineral deposits or other debris. Some older expansion tanks lack the internal bladders used in newer models. This component is what separates the water and air pressure.

Why is my expansion vessel leaking?

A common cause of water dripping slowly from a leaking boiler is a failure in the expansion vessel, or water dripping from the auto air vent in the boiler. The expansion vessel acts as a buffer for the boiler when the pressure gets too much. … As mentioned, this pressure is usually transferred to the auto air vent.

How often should you replace an expansion tank?

Between five and 10 years is the average lifespan of your tank. If your home’s water pressure matches the air pressure in your expansion tank, you can extend the life of your tank.

Will an expansion tank increase water pressure?

The expansion tank contains air, which is highly compressible. Expanding water from the water heater can flow into the expansion tank, where the air compresses, making room for the increased volume of water. Water pressure in the system doesn’t increase significantly.

What is a GREY expansion vessel used for?

Expansion vessels are small tanks used to protect closed water heating systems and domestic hot water systems from excessive pressure which can become hazardous otherwise.

Is it cheaper to have hot water on constant or timed?

It is a myth that leaving your hot water on all of the time will save you money. Unless you need a constant supply of warm water, your boiler will be constantly heating when there is no real need. It is cheaper and more energy-efficient to switch your boiler on, only when you need the hot water.

Is a system boiler cheaper than a combi?

The system boiler is cheaper than a combi boiler but still more expensive than simply repairing your old system. System boilers reviews prove that they’re cheaper and better. Typically the costs for sealed combustion boilers are higher than for traditional atmospherically vented boilers.

Can you use a system boiler with a vented cylinder?

Vented cylinders are traditionally installed with regular boilers as water is delivered to these via a cold water tank in the loft. Due to the absence of these tanks in system boiler setups, an unvented cylinder should be used instead.