Hot Water System: Lagging the Water Tank

Hot-water System:

There are many ways of heating water for household supply. The water may be heated in a back boiler fitted at the back of one of the fireplaces; it may be heated by an immersion heater running on the electricity, by gas or by a boiler fire. Whatever the method of heating the water the system of supply is very much the same for all types of homes, with an automatic circulating action as illustrated in Image 1 (below right). When water is heated in a container — in this case a boiler — the hot water rises from the boiler to the top of the cylinder and the cold water in the bottom of the cylinder flows into the boiler. Normally a hot-water system has three parts, boiler, cylinder and supply tank.

hot water systemThis diagram shows how these are arranged in the house. The cold water from the storage tank at the top of the house flows down into the cylinder, then down again into the boiler, is heated by one of several different methods, and rises when hot back into the cylinder, the circulating action being repeated as the water in the boiler is heated sufficiently to cause it to enter the cylinder. From there it is drawn off by the several hot taps in the house. From the top of the tank runs a steam outlet, so that should the water become too hot the steam is drawn off from the cylinder and taken back into the cold-water tank.


Lagging the Water Tank:

If the storage tank is in the roof-space, it is essential that it is protected against frost. The best method of doing this is to enclose it in a wooden box, leaving a space between the covering and the sides of the tank, which can be filled with lagging. The construction of a simple encasement box for a water storage tank is illustrated in the image below. The framework consists of 2-in. by 1-in. softwood battens, and the covering material can be 1/8 in. thick hardboard, or 4-in. by 1/2-in. tongued-and-grooved matchboards. The framework should be fitted to the joists upon which the storage tank rests in the roof-space, but before the framework is fitted to the joists the spaces between the joists under the tank should be filled with an insulating material; this may be crumpled newspapers, glass wool or vermiculite granules, which are obtainable from local builders’ merchants.

lagging water tanks and pipes

The box should be constructed to allow a space of at least 2 in. all round the outside of the tank and the inside of the encasement covering material. This space should be filled with any of the insulating materials mentioned above. The cover of the box, made from the same materials as the box, should be made to fit snugly over the sides of the box (see Image 2 above), and the main function of the cover is to prevent dust settling on the water in the tank. The cover should be so constructed that it does not interfere with the movement of the ball-cock lever, also provision must be made for the steam-escape pipe which acts as a safety device from the hot-water cylinder. The steam pipe has a curved top projecting over the tank (see image 2).

If the hot-water system becomes too hot, pressure on the cylinder is relieved by the escape of steam through this pipe. The steam condenses in the cooler air over the storage tank and the surplus moisture drips down into the water in the tank. A simple form of provision for this factor is  illustrated in the image above which shows how a metal or (preferably) a plastic funnel can be placed in a hole drilled in the cover under the steam-escape pipe.

Alternatively the sides of the tank may be lagged with a lagging jacket. The cover of the lagged tank should be made in the same way as the cover for the boxed tank, to allow free movement of the ballcock lever, and to make provision for the steam escape pipe. The pipes to and from the tank also require lagging if full protection against bursts is to be given. By lagging tank and pipes, not only are they protected against freezing in the winter, but the water is kept cool in the summer. If the hot-water pipes and tank are lagged this keeps the temperature of the water up and saves on fuel bills.


How to Prevent the Water Pipes Freezing in Cold Weather

Lagging Water Pipes:

There are various ways of lagging pipes, but the easiest is to wind lengths of hair felt round and round the pipe, binding it tightly with string at intervals. The felt can be bought in rolls ready for the job, and as this hair felt has been treated to make it vermin resistant it has the advantage over newspaper or the use of rags, which may encourage vermin.

Commence by wrapping one end of the felt round the pipe, and tying it securely with string. Continue winding, overlapping the felt each time, and pulling it tight. Bind and tie string round the lagging about every 12 in. along the pipe. Several thicknesses of newspaper can be used for this job, or old rags, but these substitute materials are not so neat looking and do have the disadvantage of attracting vermin.

If there are any outside water pipes these should be protected against frost as illustrated in Image 2 above. The pipe should be lagged with hair felt and boxed in with a space of about 2 in. between lagging and box. This space should be packed with sawdust or vermiculite granules.

03. July 2011 by admin
Categories: Home Maintenance, Mains Services, Water | Tags: , , | Comments Off on Hot Water System: Lagging the Water Tank


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