Once a luxury in its own right, the bathroom is now an area in which many householders indulge their taste for the luxurious. Yet, when they contemplate refitting the bathroom, surprisingly few people think of the one fixture that makes a really tangible contribution to bathing comfort: a heated towel rail. As well as providing warm, dry towels at all times, a towel rail is among the most convenient ways of drying and airing washing. It is also an excellent means of fighting that familiar bathroom problem, condensation. A heated rail warms the atmosphere in the room and raises the temperature of wall and ceiling surfaces above dew-point (the temperature at which water condenses).
Types of heated towel rail radiators
Heated towel rails come in all shapes and sizes, and vary widely in their complexity. If your bathroom already contains a radiator, all you need do is measure it and then buy one of the clip, clamp or hang-on rails that are available. Though not heated directly, these enable you to dry and warm towels in front of the radiator without impeding its main function. Next on the list are electric towel rails-self contained units (generally oil-filled). These come into their own where it is either difficult or impossible to plumb in a hot water rail. Installing the supply for an electric towel rail is done in the same way as a bathroom wall heater, but you will need a qualified electrician to wire the electrical power point.
Hot water towel rails are by far the most popular type. The plain tubular sort offer plenty of towel hanging space and generally produce enough heat to keep the average sized bathroom at a constantly comfortable temperature. They are plumbed in to the house hot water system rather than the radiator circuit, so that they remain hot even when the heating is switched off. And, as most bathrooms have a hot water cylinder close at hand, this makes installation straightforward.
Some hot water rails include a radiator panel to provide extra heating facilities, but these can be fitted only to indirect type heating systems where there is no risk of them becoming clogged with scale. Tubular rails, on the other hand, can be installed in an hot water system-direct or indirect, which incorporates a storage tank/ boiler/hot water cylinder arrangement.
Identifying your water system – Central Heating
Before you plumb in a hot water towel rail, it is obviously important to know what type of hot water system you have and to identify the pipes. In the older, direct system, water heated by the boiler rises by thermal convection to the hot water cylinder. Here, it continues to rise until it passes out of the top (crown) to the hot taps, via the hot water supply pipe. Fresh water is fed to the system from the cold storage tank and enters via the base of the cylinder.
From here, it sinks to the boiler under force of gravity. If no water is drawn off the hot taps, the water in the system continues to circulate between the cylinder and the boiler. When hot water is used, fresh water is taken in and heated to the desired temperature. Although simple, the main drawback of the direct system is scale. This is released every time fresh water is heated above about 60°C and clogs cylinder and boiler pipework alike. In the indirect system—most often found with central heating—the problem of scale is avoided by having two separate circuits. The first—known as the primary circuit—runs continuously between the boiler and cylinder. The water in it is always hot, but because it is never drawn off it needs to be heated only once.
Consequently, it releases its scale the first time it is heated and from then onwards it is relatively scale-free. The hot water cylinder in an indirect system contains a loop,the heat exchanger, through which the hot primary circuit water passes. As it does so, it transfers its heat to fresh water fed to the base of the cylinder from the cold storage tank. This fresh water then becomes hot—but not hot enough to release scale—and rises out of the crown of the cylinder to feed the hot taps in the normal way. The cold feed, the outer part of the cylinder and the pipework supplying the hot taps comprise what is known as the secondary circuit.
Both direct and indirect systems contain vent pipes to guard against the build-up of excessive pressure. The direct system has a single vent pipe, rising from the crown of the cylinder, or the hot tap supply pipe, to above the cold storage tank. The indirect system has this pipe too, plus another rising from the primary circuit flow pipe to above the expansion tank. The function of the expansion tank in an indirect system is to top up the water in the primary circuit, should some be lost by leakage or evaporation, and to allow for the slight expansion of the water as it is heated. The flow in the primary circuit may be by gravity—as in the direct system or included in the radiator circuit and under pump pressure. In the latter case, a motorized valve distributes water from the boiler between the cylinder heat exchanger and the radiators as and where it is required.
Connecting the towel rail radiator
Hot water towel rails work on the same principle as radiators, with two connection points for flow and return pipes. In both direct and indirect systems, pipes can run from these to intercept the hot water flow pipe between the boiler and the hot water cylinder. This pipe is cut, and T shaped connectors inserted to make the final connections.
Obviously, it is absolutely essential to know which pipes are which before you connect to them. This may call for a bit of detective work particularly in the case of an indirect system, before you go any further. But in any case you should aim to make the connections somewhere around the hot water cylinder. Here, the pipes are easier to identify.
Most direct cylinders have four pipes running from them. Of the two near the crown, the lower is the flow pipe from the boiler which supplies the cylinder with hot water. The other is the hot water supply pipe, which supplies the hot taps and generally also holds the vent pipe. In some cases, the vent rises directly from the cylinder (in which case there will be a total of five pipe connections). Of the two near the base, one is the cold feed from the cold storage tank and the other is the return taking back cooled water to the boiler.
Indirect cylinders have the same hot supply vent pipe at the crown and cold feed at the base as direct ones. But the primary flow and return pipes to and from the boiler generally run into the side of the cylinder and stand out from the rest of the pipework. An additional complication is the primary circuit vent pipe. This may pass near the water cylinder, or it may be connected to the flow pipe.
About the only safe way to identify the pipes is to trace each one in turn and then lable it clearly somewhere near the connection point. Once you have the found the flow and return to the boiler, search for a suitable interception point on the flow pipe. This should preferably be on a straight, horizontal run. Make sure, too, that there will be room to work and that the pipe route to the rail will not be too tortuous.
Once you have decided on a site for the rail and identified the connection points, you are ready to begin installation. On all types of hot water system, the first job is to turn off the boiler and allow both pipes and cylinder to cool down. What you do next depends on the type of system.
In this case it is preferable to turn off the cold water supply at the cold storage tank— rather than at the rising main so that you will still have use of the kitchen cold tap. If there is no stop valve, tie up the ball valve in the closed position. Drain the cold tank by opening all taps fed from it, then drain down the hot water system. Attach a hose to the drain cock, which should be located adjacent to the boiler in the return pipe, and having placed the other end of the hose at a suitable drainage point, open the cock. With the cylinder empty, the hot water flow pipes can be cut using a fine toothed hacksaw and the T-shaped fittings connected.
Since only one radiator/rail is to be served, the pipe runs from the teeing points to the site of the unit can be safely made in 15mm copper tube. Assuming that the bathroom is on the first floor, and the floor itself is a conventional joist and board structure, the pipes should run by the shortest possible route under the floorboards. If they must run across joists, notch them into the tops of the wood joist. Where changes of direction are necessary, use elbow compression fittings or bend the pipe with a bending spring. If running the pipes under the floor is not feasible, soldered capillary fittings are less obtrusive and cheaper than the compression type.
Where changes of direction are necessary in surface piping, bend the pipe in preference to using bulky ready-made fittings for a neater finish. If the bathroom is on a solid ground floor, it may be possible to run the pipes in the ceiling void, then down to connect to the towel rail. The connections to the rail are made with normal radiator valve fittings, a wheel valve with a turntable head on the flow (hot supply) side, and a lockshield valve with a screw-fixed cap on the return side. These compression joint to the pipes, which must be cut to length once the rail is in place. Unlike radiators, which are usually hung on brackets fixed to the wall, towel rails—including those incorporating radiator panels are fixed to the floor by screws passing through their flanged feet. Some also have flanges at the top so that you can fix them to the wall for added stability.
With the unit fixed and the connections made, check that all taps and drain cocks are closed, open the air vent normally located under the top rail of a towel rail—and restore the water supply. As the system fills, watch for water appearing at the rail vent. When it does so, close the vent, restart the boiler and run it for about half an hour. Then re-open the vent to release any trapped air in the towel rail itself, with a small pot under the valve to catch any water.
Here, there is no need to shut off the water at the main cold storage tank or drain the hot water cylinder. Instead, cut off the supply to the expansion tank, attach a hose to the central heating system drain cock which should be located on the boiler return pipe at its lowest point and open the cock. The water in the system should contain rust-inhibiting chemicals, and you may feel it worth collecting the drained water in containers to be put back into the system when you refill it rather than buy a new supply. Having drained the system completely, proceed as for a direct hot water system. When the installation is complete, refill the system by restoring the cold supply at the expansion tank. After filling, turn all your radiator valves to the fully open position and bleed the radiators in turn to remove airlocks. When you are opening lockshield valves, count how many turns it takes, and afterwards close them by the same number.
You may find that the system needs further bleeding after several days, but this is perfectly normal.