Frequently Asked Questions
We have put together a list of frequently asked questions that many of our customers have asked us over the years.
We hope you find the answer you need here, but if not, please contact us.
3. What to do if the top of radiator is cold and the bottom hot?
This is normally due to a build up of air in the radiator.
This can usually be cured by bleeding the radiator using a key. Have a cloth ready to catch the drips as the water can be dirty.
4. What does it mean if the top of the radiator is hot, and the bottom cold?
This can be more of a challenge. This can occur on older systems and is often due to a build up of sludge or Magnetite in the bottom of the radiator. Excessive deposits in a central heating system indicate that the water has not been treated with a corrosion inhibitor over the life of the installation, or perhaps the inhibitor has been emptied at some point and not topped up? Other indications are noisy pumps sticking, valves poor warm up times, intermittent radiator warm up and boiler overheating. Although it is often possible to effect an improvement by adding a chemical ‘central heating restorer’ to the system or disconnecting the radiator and flushing it outside with a high pressure hose. However, ultimately the most permanent remedy is professional flushing & cleaning. Call Surefire Plumbing for a quotation, or click here for more information on powerflushing.
5. Some of my radiators are cold but when I try to bleed them no water comes out?
This can be caused by an airlock. Try turning all the other radiators in the house off (using the radiator valves noting the number of turns each time) and then try bleeding. Reset the valves to their original positions when you have finished (see below regarding ‘balancing’). Alternatively, sometimes central heating systems suffer from a ‘blocked cold feed’ which will gradually cause the system to run out of water because it isolates the water feed and expansion tank from the radiators, pipework, boiler & controls. Repairing a blocked cold feed is not a DIY proposition. Call Surefire Plumbing to request a service engineer visit.
6. How to balance performance throughout the house on different radiators?
This can be achieved by adjusting the lockshield valve (usually covered with a plastic cap) to adjust flow of water to all the radiators in the property. Professionals usually set these up by checking the temperature differential across the inlet/outlet pipes; however a more basic balance can be achieved by reducing the flow to those radiators nearest the heat distribution point (normally the pump) and opening the valves to a greater degree on those radiators furthest away.
7. My central heating has started coming on with my hot water (whether I like it or not)?
This is usually down to a failed motorised valve (on a conventional cylinder/boiler system). My combination boiler will only deliver hot water when the central heating is on! This is usually a fault within the diverter valve mechanism; this is not a DIY job. Call us and advise the boiler/system type for an idea on costs.
8. What to do if water is leaking from the cylinder?
Copper water cylinders have a varied lifespan; if the water is leaking from the bottom of the cylinder the only practical remedy is a replacement. Copper water cylinders have a varied lifespan; if the water is leaking from the bottom of the cylinder the only practical remedy is a replacement. Please contact us for a quotation.
9. How to re-ignite boiler if pilot goes out?
On most modern boilers the pilot comes on automatically when the boiler detects a ‘call for heat’ from a room thermostat or hot water thermostat. If this is not happening, please call Surefire Plumbing.
Some older types of boiler have a ‘permanent pilot’ light. This is designed to stay burning 24 hrs a day, 365 days a year. It may go out for a number of reasons, such as an interruption in the supply (someone turned it off?), a draught, or a fault with the boiler. Before calling professional help, it is usually worth attempting to re-light the pilot yourself (the manufacturer usually prints lighting instructions on the inside of the door). If the pilot goes out again soon after being re-lit, you should call us, as professional attention is required.
10. How often to service a boiler?
It is prudent, for safety and efficiency, to have the boiler serviced annually.
Surefire Plumbing charges £98.00 + vat for this & we include an electronic test of the boiler emissions using specialist equipment which checks the level of Carbon Monoxide produced within the boiler.
11. What is the danger if the boiler is not serviced regularly?
Surefire Plumbing, as with most Gas Safe registered technicians, have personal experience of the dangers of not looking after gas burning appliances. We have come across a number of instances where faults have lain undetected due to lack of maintenance and have resulted in carbon monoxide poisoning of the house occupants. In severe cases lives are at risk & some have been lost. Drowsiness, nausea, headaches are all symptoms. If you live in rented accommodation, the Landlord is legally obliged to have a safety inspection carried out annually. You can ask to see the inspection certificate at any time. If you are a Landlord, please bear in mind that most contractors performing ‘CP12 inspections’ or ‘safety checks’ do not check the internals of the combustion chamber or clean the unit internally. An annual CP12 is not a form of maintenance for your boiler. The best analogy is a car; no-one would expect their car to run properly by purely submitting it for the annual MOT. Surefire Plumbing electronically test the products of combustion to ensure the safety of your tenants.
We charge £98.00 + vat for this service.
12. Should my boiler be set higher in the winter?
For conventional boilers, during the winter the boiler thermostat should be set higher than the summer. It’s best not to run the boiler indefinitely on the highest setting – unless you have a ‘thermal store’ (see below).
13. What to do if you smell gas?
Turn off the gas supply at the meter. Open windows but do not turn any electrical items on or off.
Call Southern Gas Networks (SGN) immediately on 0800 111 999.
If the leak is on your pipework/equipment (the customer side of the meter) SGN will normally turn off the supply and advise you to contact your local Gas Safe registered engineer. Call us and we will attend asap.
14. How many radiators needed per square foot/room, etc?
This is a calculation based upon a number of variables. Room size, height, and type of insulation & flooring type, all need to taken into consideration. Where there are limited positions available to site a radiator in a larger room, consider a ‘double’ convector unit rather than the usual single type. In kitchens where space is limited, consider an underplinth fan assisted unit, such as a ‘Myson Kickspace’.
15. What are the benefits of radiator thermostats?
The use of Thermostatic Radiator Valves prevents individual rooms being ‘overheated’. Without TRVs the only temperature monitoring and control is done by a room thermostat; this covers the whole house rather than an individual room. Some rooms tend to warm up quicker than others, thefore a TRV can maintain comfort while potentially aiding economy. The new building regulations stipulate that on new installations and upgrades, TRVs should be fitted to sleeping areas. NB: Cheaper TRVs can get stuck over time, so it is worth buying a premium brand (eg: Drayton, Pegler or Honeywell).
16. How long will an average boiler last?
This very much depends on the type of boiler chosen, and the quality of the system it is connected to. It is usually worth specifying the best boiler you can afford, they are not all the same inside. Be wary of your contractor trying earn a free holiday in Spain by recommending and fitting budget boilers. Surefire Plumbing recommend Vaillant and Worcester Bosch products.
17. Type of boiler?
Combination boilers offer instantaneous domestic hot water as well as central heating, and as such are very convenient. However, their design is more complex than conventional boilers and the lifespan is typically 10-12 years, depending on the build quality & hardness of your water. Conventional cast iron boilers have a longer life, 20 years is not uncommon.
18. Should central heating be used occasionally in summer?
Yes, if the system is run occasionally it will prolong the life of certain components, including the pump. Some combination boilers (eg: Worcester Bosch & Vaillant) automatically run the pump & diverter valve periodically during periods of inactivity to help extend their life.
19. What is a pressurized central heating system and what are the benefits?
A pressurized system uses an expansion vessel. The main benefits are the lack of a requirement for a ‘filling and expansion’ tank in the loft, no possibility of pumping over & less corrosion & sludge build up.
20. How do I find the stopcock for my property?
Good question. It’s usually found on an internal wall, often under the sink. However some properties, typically conversions to multiple occupation, do not seem to have one! Even though they should, of course. If you can’t find an internal stopcock, an external stopcock can usually be found under a small square iron & plastic cover in the pavement. It sometimes needs to be dug out & turned on & off with a special turnkey.
21. What affect does water metering have on costs on heating systems?
If you prefer baths to showers, and water the garden regularly, a water meter may prove to be the more expensive option.
22. How often can radiators be painted and what impact will it have on performance?
It’s best to paint radiators in ‘radiator enamel’ which is less likely to discolour over time with heat. Most new radiators already come with a gloss white finish. Painting will have very little effect on performance, as most heat is by convection upwards rather than radiation outwards.
23. Can I paint copper pipes?
Yes you can, but bare/new copper should be first lightly abraded with emery cloth or wire wool, and then wiped with white spirit to remove any preservative/grease.
24. How much impact does insulation on the hot water cylinder have on bills?
It will reduce them in all cases. Modern cylinders come with pre sprayed foam lagging and are much more energy efficient.
25. What does it mean when pump is whining loudly?
It can mean that the bearings are badly worn, there is an obstruction in the flow of water, or there is no water in the system. Call us for an instant quotation.
26. How long does the hot water have to be on for water to be hot enough?
This depends what type of cylinder you have. You can upgrade to one of the latest “fast recovery cylinders” which can recover the hot water in around 12 minutes. Super fast hot water at almost half the cost of a traditional cylinder!
27. Is it more expensive to run an immersion heater relative to using a gas boiler?
Yes, in almost all cases.
28. My hot water is far too hot?
If you have a Combination Boiler there is usually a hot water temperature setting. For normal systems comprising a hot water cylinder there is normally a ‘cylinder thermostat’ mounted on the side of the cylinder which should be preset to 55-65 degrees. If there is no cylinder thermostat fitted you have an older system and the hot water temperature will be governed by the thermostat in the boiler. During winter months you may find that if you turn this down low enough for moderate temperature hot water, the radiators will not be hot enough. The only solution is to get the system design upgraded. Lastly, if you heat your water by immersion heater and the water temperature is far too hot, there is a high liklihood that the internal electric thermostat is stuck in the ‘on’ position. If you are competent with electricity then this is an easy job to change without the risk of getting wet. Note that if you leave the immersion heater thermostat stuck in the on position, this will cause the eventual demise of the immersion heater element and limescale build up in the cylinder. So change it now!
29. My hot water does not get warm enough?
On a Combination Boiler this is usually due to sludge and scale build up in the DHW heat exchanger. This is not a DIY job to rectify, and can be indicative of more far reaching corrosion problems in the system. In a normal, cylinder fed system, the ‘cylinder stat’ could be set too low. During winter months, the boiler thermostat will need to be set nearer the maximum than in summer, due to the extra demands made by the central heating.
30. In the morning, certain hot water taps do not work initially?
Sometimes this is due to system pipework design causing an airlock. A common fault is the pipework is not vented correctly where the hot water outlet comes off the top of the cylinder. Air bubbles rising from the cylinder get trapped at the top outlet causing an airlock. Once the airlock has been removed (maybe by opening a bath tap) the system will work until it has had a dormant time for the air bubbles to achieve an ‘airlock’, usually the following morning. Poor pipework layout within the property can also cause this problem.
31. What are the differences between ‘combination’ and ‘conventional’ boilers?
A combination boiler is where the boiler heats both the central heating and provides instanteous hot water without needing external tanks or cylinders. However it is worth noting that combination boilers will primarily only serve one tap at a time. Conventional /traditional boilers normally reqire a stored tank of cold water in the loft area & a hot water storage cylinder in the airing cupboard.This type of system is more suitable if hot water is likely to be required to more than one tap at a time.
32. I have a warm air system, should I change it?
The good news is that warm air central heating is quite simple and there is not much to go wrong. The bad news is that for some of the older systems there are significant numbers of parts no longer available. There are only one or two manufacturers of domestic warm air systems left in the UK, and there has thus been very little technical innovation in the last 20 years. Many old warm air systems have now been removed and replaced by ‘wet systems’ (eg: radiators). Some customers do not like the dry nature of the heating. If you require a quotation for a replacement wet central heating system please give us a ring to arrange a quotation at your convenience.
33. What is a SEDBUK rating?
This is a rating which tells the consumer how much of their gas is turned into useful heat output by the boiler (working in ideal conditions). There is still a percentage rating available, which makes more sense. This is normally stated in the manufacturers brochure.
34. What is a condensing boiler?
Conventional boilers emit hot exhaust gases from the flue when they are operating. A condensing boiler transfers much of this wasted heat to the water in the boiler, before it reaches the flue outlet. An excellent idea, which saves on fuel use and therefore operating costs. During normal operation, condensing boilers lower the temperature of their exhaust gases below 100 degrees, at which point plumes of water vapour can be seen coming from the flue outside. For this reason condensing boiler flues should be sited sensitively. Whilst there are gas consumption savings to be made from a condensing boiler, their actual efficiency is dependent upon the system design of the heating circuit. A condensing boiler is more complex to manufacture and this is reflected in the higher purchase price. Some experts say that the payback period for a condensing boiler can be 3 years. For more information on pluming see Question 40
35. How long does it take to install an average system?
This is very dependent on the type of house. However, in order to minimize disruption, we always endeavour to put more manpower on larger jobs so that the customer inconvenience is kept to a minimum. How long can I expect to wait for parts, if they are required? This varies enormously between manufacturers. Generally speaking, the older the boiler the more difficult spares are to obtain.
36. What does Gas Safe registration imply?
The Gas Safe registration implies that at least one of the operatives of a company/partnership has achieved the technical proficiency in order to handle Gas Safely. It is ILLEGAL for a non-registered individual to work on any gas appliance. A company’s Gas Safe registration does not guarantee fair trading or value for money, Gas Safe’s remit is promoting and maintaining Gas Safety and standards.
37. I’m a Landlord, what responsibilities do I have with respect to gas appliances?
You must have all gas appliances inspected and certificated once per year. It would be advisale to have the boiler serviced periodically too.
38. What is a ‘thermal heat store’?
This is where a large quantity of preheated water is kept in a highly insulated container. This water is then used to indirectly (eg: by heat exchange) warm up cold water, on demand. If you know how an ordinary hot water cylinder works, the best way to describe a heat store is ‘its a HW cylinder working in reverse’. The water in the cylinder is boiler fed and kept hot 24 x7; cold, usually mains fed water is passed up the primary coil and emerges at 55 degrees the other end. Because it’s mains pressure, no shower pumps, etc, are required. If you have a larger house one of these offers the convenience of a combi but the reliability and flow rate of a tank fed system. Disadvantages are space and cost.
39. What does ‘unvented cylinder” mean?
“Unvented” is a term used to describe a hot water cylinder which provides hot water to several taps simultaneously at high pressure without the need for stored water in the loft. This is an excellent way of handling your hot water needs to several taps at a time at high pressure, without the need for a mechanical pump. It is however usually the most expensive option.
40. What is ‘plumage’?
Plumage is the term used for the flue gases produced by condensing boilers.
Because the “plume” is much lower in temperature than the flue gases produced by a less efficient boiler, and is concentrated in water vapour, it is much more noticeable (appears similar to steam). To avoid the potential nuisance of plumage boiler manufacturers have developed highly versatile flueing options. So instead of replacing the boiler in the kitchen for example, we can resite the boiler almost anywhere in the house (airing cupboard, loft, garage etc). This means that in almost every home the nuisance can be avoided.