A husband and wife team keeping Dorchester's boilers, fires and taps going since 2005.

Not if you don't need to. There are plenty of old boilers, by which I mean standard efficiency, cast iron, balanced flue appliances that have chugged happily away for 20 plus years and can go for another 20 without any problems. Other parts of the system, the pump and motorised valves may need replacing during that time.

Routine cleaning of the boiler is really all that the boiler requires and the occasional new thermocouple, a very inexpensive part compared to modern boiler components, sometimes a new gas valve. Yes, they are not as efficient or compact as modern boilers but efficiency, although always a good thing, is not the same as cost efficiency. Beef up your home insulation instead.

Where I do remove old boilers is when they are no longer safe, usually when the flue has rotted and products of combustion are spilling, or when the homeowner can no longer put up with the cold draught through the open-to-air vents that cannot be blocked.

My usual answer is: the one with the longest guarantee, with the caveat that the guarantee is provisional on the appliance being installed to the manufacturer's instructions, registered with GasSafe and the manufacturer, and an annual servicing has been carried out and recorded in the Benchmark book that came with the boiler. It is well worth keeping the maintenance up to date because, like for modern cars, the price of boiler parts is eye-watering.

All modern boilers are much of a muchness really and, in my opinion, better than they were a few years ago. My personal preference currently is to fit Ideal Vogue boilers because I prefer stainless steel heat exchangers, the guarantee is good and most importantly I hear very little mention of problems with this model on the plumbing grapevines. I also like to upgrade the controls using the boiler manufacturer's own stuff because they have been designed to work together, they speak the same digital language.

Whichever suits the hot water requirements of the property. The latest combi boilers have a very high hot water output but they do require much larger gas supply pipe than older equivalents. Unvented cylinders/megaflo: always better in my opinion than old cisterns in the loft and a copper cylinder but they do require space and a degree of regular maintenance.

Know where they are, what they do, label them and every so often turn them off and on again. Left alone, they will seize and you need them to work when you need them to work, often in a hurry.

Ballofix valves, the little ones that are turned with a flat screwdriver: I don't fit them, they leak and do all of my customers have a flat headed screwdriver handy if water is spraying from a burst flexi? No. Fit full bore lever valves.

Unfortunately, many modern taps, suitable for high pressure supplies, can only be connected to the pipework with these things. Check them for any signs of rust. If they are rusty they will fail and flood your home. Use only good ones from a reputable manufacturer and connect them to a lever valve using flat face tail adaptors.

Every so often turn the valve head, especially during summer when the radiator is off. They do seize up if left alone.

Yes, but only when it's done by the book and this means, among other things, recharging the expansion vessel inside the boiler, often overlooked.

Many modern boilers require the combustion seal to be replaced every time the boiler is opened up for servicing so please let us know the make and model so that we have the seal on the van before we arrive.

Why wouldn't you. Most new boilers require them. They don't stop corrosion; a well installed system and chemical inhibitor does that, but they protect the most expensive part of the system, the boiler, from the products of corrosion.

Proper ones that is, not the silly in-line magic mirror thingies. Dorchester sits on top of a hill made entirely of scale, chalk/calcium carbonate. I've got one.

The Beast from the East. Kept me busy. Insulate pipes in the loft and turn off your garden tap from the inside and drain out the residual water.

Boiler condensate pipes run to the outside need lagging or oversizing to prevent freezing. If they freeze the boiler will stop working. If you are defrosting them yourself, do it gently: a towel soaked in warm water is safer than a boiling kettle.

Back in the day a dripping tap needed a new washer. The washer seating would be re-ground smooth, the washer replaced and the valve popped back in. I have found that common or garden basin taps nowadays often can't be repaired because the valve seating that I would have normally re-ground has split making the tap unrepairable. They really don't make them like they used to.

Ceramic disc taps can't be re-washered, they require a new cartridge. If you don't know who made the tap it is very difficult to get the right cartridge. If you are splashing out on a shiny new kitchen mixer it is worthwhile purchasing a pair of replacement cartridges, hot and cold, at the same time.

Contrary to what you might expect, it is better to oversize a radiator nowadays when replacing one. This does not mean a bigger radiator per se, but one with a higher output. This is because fitted with a TRV the flow rate through the radiator will reduce as the room temperature rises and also because, if you have a new boiler fitted, the temperature of the water running through the radiator can be much cooler than you think it should be.

Modern boilers modulate the rate at which they burn gas to optimise their efficiency and with modern controls to match the air temperature inside (and sometimes outside). They aim to meet and keep the temperature you have set at the room thermostat without going over and having to switch off and then back on again which, like a stop/start traffic jam, is wasteful.

So, if you have a new boiler and the radiators don't feel hot they might not need to be hot to keep the air temperature warm. Then again, they could need bleeding or be blocked.