A vented hot water cylinder is also known as a gravity-fed hot water cylinder. This is because the vented cylinder works on a gravity system by having the water supplied from the cold water tank, also known as a header tank, which is often stored in the loft or on a higher floor, as the system relies on gravity to build pressure.

The name 'vented hot water cylinder' is because the 'open vent' is a pipe which acts as a safety mechanism releasing built-up pressure. The vent pipe runs from the cylinder back up to the feed and expansion tank, releasing the built-up water pressure in the tank to stop the system from overheating. Vented cylinders often are made of copper or stainless steel and a cheaper system to install than an unvented system.

When should I choose a vented cylinder?

If it is time for a heating engineer to replace your vented hot water cylinder, the easiest installation is usually going with a similar set-up to what is already installed needing replacing. This will be because the pipework is in place, ready for the cylinder to just be swapped out for a newer version.

Older UK properties tend to have vented cylinders. This means the pipework plumbed in throughout the home, was designed for a low-pressure system. Replacing the hot water cylinder with a different set-up may require pipework to be replaced to handle the higher pressure of a pressurised system. This of course would add to the installation costs.

Choosing a vented cylinder will need a home that has a loft space for the header tank or an upstairs storage space as the cold water tank does need to be positioned high enough to create the pressure from gravity for it to work best.

If the mains water pressure supply from your road into your home is low, your system will benefit from replacing the cylinder with a vented cylinder. This way gravity can help create a better water pressure. A vented hot water cylinder can either be heated directly by an immersion heater in the cylinder or indirectly by a boiler. A lot of UK homes rely on a gas boiler to indirectly heat the water but still have an immersion heater as a backup in case of a boiler breakdown.

Can I fit a pump on a vented cylinder?

If your vented hot water system is struggling to maintain pressure, it is possible to fit an electric pump to the vented cylinder. A heating engineer can fit a shower pump to the system to improve the water pressure from a gravity system.

When it comes to improving the pressure and fitting a pump, there are numerous options of pump styles to be fitted to the water supply;

• Small twin-impeller pump for a single shower
• Larger pump to supply better water pressure to all of the taps in a bathroom, not just the shower
• Centrifugal pump to supply the entire home with a stronger water pressure

How much will it cost to install a vented hot water cylinder?

Replacing a vented hot water cylinder is not too expensive a job. Including the cylinder and labour, this could cost from £500 because if replacing” like-for-like”, the job may be able to be completed in less than 3 hours. The more complicated the job, the longer the heating engineer will need on site but still should only be a day's labour charge to fit a new vented hot water cylinder.

Image	Name	Cost
	Gledhill Indirect S/Steel Cylinder 815 x 450mm, 120 Litres	£256.00
	Telford 900 x 450 Indirect Vented Copper Cylinder	£294.00
	Gledhill Indirect Copper Cylinder 900 x 450mm, 120 Litres	£358.00
	Telford Indirect 105L Combination Copper Cylinder	£415.00
	Telford 1500×450 Solar Twin Coil Indirect Vented Copper Cylinder	£567.00
	Gledhill Indirect Copper Combination Cylinder 1200 x 450mm	£579.00

How do I know if my vented hot water cylinder needs replacing?

A vented hot water cylinder should last 10 - 15 years before needing replacing. Of course, the length of time depends on how well it has been maintained.

If you start noticing signs of leaks, the cylinder might be cracked or have a pin-hole and may need replacing.

Limescale can build up in the cylinder over the years and this can cause blockages as well as cause the cylinder to not heat effectively or make noises.

If the water from hot taps only is coming out with a smell or discoloured, this could mean that the heat exchanger inside the cylinder has burst and hot water and heating water are mixing. This is dangerous and would mean that the cylinder needs urgent replacing.

Another reason for discoloured or smelly water can be the result of the cylinder's anode rod corroding and that part might need replacing or the entire cylinder replacing.

Which is better, vented or unvented?

When it comes to wondering which out of vented and unvented cylinders is better, vented cylinders require almost no maintenance and are a simpler system to install, therefore often resulting in a cheaper choice. As already mentioned, older UK homes are already plumbed in for vented cylinders so all that is needed is a ‘like for like’ replacement rather than the expense of upgrading plumbing for an unvented system.

Other advantages of vented systems include;

- If the roads water supply is cut off, then the header tank should have a full supply of water, keeping you going until the roads water supply is fully restored

and

- Consistent water pressure and supply when mains pressure is low due to high demand

The only major downside is the space needed for the header tank in the loft.

Of course, unvented systems have their advantages too, mains pressure hot water will generally have a better flow rate (provided the mains supply is strong) and youn gain space without needing the tank in the loft.

Estimates for common heating engineer jobs;

Rates for other trades