Hot water tank repair costs explained

What is the industry average?

There are a number of faults which can arise with a hot water cylinder and the water tank repair cost will depend on the nature of the fault. The easiest way to price it is to work out how much a heating engineer or plumber charges per hour – an industry average to work to is £45 – and the hot water tank repair cost (or replacement) will be the amount of time it takes them to find the fault, repair it plus any materials required.

What type of water tank do you have?

Water tank repair costs can often be influenced by the type of cylinder you have. Here are two types of hot water cylinder – vented and unvented.

• Vented hot water cylinder – a vented cylinder requires a supply of water from a large cold water header tank which is usually located in the loft. Gravity is used to direct the water down through a vent pipe to the hot water cylinder which is on the first floor and commonly located in the airing cupboard. The water is heated within the tank by a hot water element and the vent pipe also acts as an escape route for any excess water from the cylinder.
• Unvented Hot Water Cylinder – unvented cylinders don’t require a cold water tank in the loft because they are directly connected to the mains. The flow of water from the mains is under pressure and so there is no requirement for gravity to feed water into the tank. Because of the absence of a vent pipe, unvented cylinders have built in safety features in case of an escape of water – this will either be an expansion unit at the top or an air bubble that gets added during the installation.

What are the problems that can occur with a hot water tank?

There are lots of problems which can arise and dependent on the hot water tank repair, this will impact on the cost. Here are some of the most common problems:

• No hot water – and always at the most inconvenient moment. If you have a gas-powered boiler then your first port of call should be to check that the boiler is igniting property. If the pilot light is out then it might just be a case of calling a Gas Safe registered engineer if you can’t relight the pilot light. If the system is powered by electricity so this is an immersion heater, check the power supply at the trip box or RCD (Residual Circuit Breaker). It may be that the circuit for the tank has been tripped off by an electrical problem elsewhere in the house. Having established that the power source is still working then it could be that the tank is leaking somewhere in which case this will need to be assessed and repaired by a plumber or heating engineer
• Not enough hot water – check the temperature setting on the cylinder. It might just be the case that the cylinder is not large enough to meet the demands of the household, a point to consider if you are extending your home or converting the loft. If you live in a hard water area then your cylinder, if it is quite old, could just be full of limescale which reduces the available space for the water but a lack of hot water can also be caused by a leak
• Water too hot – check the temperature setting first, if it is correct then there could be an issue with the temperature pressure relief valve not shutting off when it reaches the required level. The valve may need replacing and this can be a serious issue as the taps will release scalding hot water to the unwary
• Discoloured or smelly water- the cause for this can vary depending on whether the issue is with the cold or the hot water feed. If it is both hot and cold water or just the cold, then the issue will be emanating from the mains supply and not the cylinder. If the hot water only is discoloured and/or smelly then this indicates a problem within the tank itself and this can be the result of the anode rod deteriorating in combination with water which has a high concentration of sulphates. The solution is to flush the cylinder or you may need to replace the anode rod. The anode rod protects the lining of a hot water heater from corrosion
• Strange noises – most water tanks will make some sound as the water heats even as much as the odd whine or gurgle. However, as sediment builds up, you can experience blockages with lumps of scale which can cause this. Ask an engineer to clear and flush the tank regularly to prevent build up and noise
• No water at all – this is probably an issue with the filter which could be blocked and this is a job for a heating engineer to resolve. Or you may have a leak

How much does it cost to replace the actual cylinder?

If the job is a straight cylinder for cylinder swap, then this will usually take one days’ labour. As well as the cylinder there will be secondary materials such as washers and fittings and the cost of disposing of the old tank and any other waste created during the job.

Standard copper water cylinders are around £200 although you will pay more if you want a larger capacity or any added features. With the labour at an average rate of £45 per hour, the entire job should cost in the region of £600 without any VAT which could be an additional cost.

How to look after your hot water cylinder

Surprisingly, there are things that you can do to help prolong the working life of your hot water cylinder and reduce those unneccessary hot water tank repair or replacement costs. Here are some tips and suggestions:

• Adjust the thermostat to 120 degrees – you will save up to 5% in energy costs for every 10 degrees you lower the temperature plus you reduce the risk of scalding
• Drain the tank two or three times a year to remove sediment and debris particularly if you live in a hard water area. Turn off the cold water supply at the stop cock, hook up a garden hose to the drain valve then run off into a bucket until the water is clear. If the water remains cloudy then open up the water supply valve again to stir up the remaining sediment and repeat the process and drain the tank again. You can ask a heating engineer to flush through the tank if you prefer but it really is quite simple and there are lots of online tutorials which can show you how to do it safely and without a mess. It will also make the tank quieter if it has been getting noisy
• If you live in a hard water area then fit a water filter to the house water supply, this will reduce the amount of limescale which builds up inside the tank
• Insulate older units with a fibreglass jacket – newer units are pre-insulated
• When you go on holiday, adjust the thermostat right down on the boiler which maintains the pilot light but doesn’t heat the water

FAQs - Hot Water Tank Replacement Costs

Should I repair or replace my defective hot water cylinder?

The answer to this depends on the nature of the fault and the age of the tank. If the hot water tank repair is likely to be costly and the tank is old, it may be money better spent to put towards a new tank. An old tank would be considered to be a tank which is ten plus years in age although if a tank is well looked after and not the victim of hard water then they can last 15 or as much as 20 years.

What is the warranty period on a new hot water tank?

The usual warranty period is five or six years irrespective of whether the heat is gas or electric. There are more expensive units available with longer warranties which can be up to ten years.

Should I call a plumber or a heating engineer to repair my hot water tank?

You can call either but if you have a gas-powered boiler and the fault is with the actual boiler, then a plumber will not be able to repair this, the boiler can only be looked at by a registered Gas Safe engineer.