The Joints used for cast-iron hot-water pipes may be said to be confined to the borings joint, red and white lead, and rubber collars. The borings joint, also known as the rust joint, is made as follows:-Mix well together in a dry state 80 to 100 parts by weight of iron borings, two parts of flour sulphur, and one part of powdered sal-ammoniac. The borings can be obtained very cheaply from factors who supply the pipe ; and they should be beaten small if very coarse. Afterwards mix all with sufficient water to moisten the whole, but not to make it very wet. This should be done an hour or two before it is required for use. In making the joint, the yarn or gaskin is cut into lengths sufficient to make about three turns round the pipe, and this is caulked in, length by length, until the socket is about three-fourths full. It may be explained that the joint, so far as keeping the water in, is made by the yarn, while the borings mixture is used only to back it up and keep the joint permanently sound. When the yarn is in the borings follow, and, while these should be caulked securely in, some care is needed, as the mixture expands a little in setting. It is this expansive action which makes the joint so firm a one, but it also cracks the pipe socket if care is not used. On this account it is best to use the least practical quantity of borings ; and while fitters have different ideas in regard to this, it will be found that a depth of three-quarters of an inch will be satisfactory. Freshly mixed borings are more liable to cause trouble than a mixture which has stood from one to two hours (according to the dryness or dampness of the weather).

Horticultural Hot Water Work Continued 87

The borings joint is seldom used when the number of joints to be made is small. In this case dry red and moist white lead are resorted to, these being mixed together to the consistency of putty. A small quantity of this putty is thinned with linseed oil, to make a paint, and the inside of the socket and the outside of the spigot end of each pipe are painted with it. A length or two of yarn is first caulked in, on top of which some of the putty is put. This is followed by more yarn and putty, alternately, until the socket is full. It is a somewhat expensive joint, owing to the cost of the lead, but not sufficiently so to be objectionable with a few joints.

A joint of intermediate cost can be made by substituting the following mixture for the lead putty :- Two parts of dry slaked lime (or whitening or chalk will do), one part litharge, two parts clean sand, and sufficient boiled linseed oil to make a putty. This is used with yarn in alternate layers, as is the lead putty.

There are several patented joints in which a rubber collar is used as the jointing medium. Some of these require both ends of the pipe to be specially formed, and some have one plain end, while Jones's joint, illustrated in Fig. 55, is used with pipes and fittings having all ends plain. This latter joint does not bear much pressure, and is therefore used wholly in horticultural works or those of limited elevation. The makers consider it suitable if the head of hot water does not exceed 25 feet.

Quantities

Being the Area of Low-Pressure Hot-Water Heating Surface required to obtain given Temperatures in Rooms and Places.

Brick-Built Structures

Temperature required when it is 30° outside.

Super. Feet of radiating

Surface per

1000 Cubic

Feet of Space.

Purposes.

Degrees Fahr.

SO

9

Coach-houses, stores, etc.

55

12

Places of worship, places of employment, bedrooms.

60

15

Living rooms, offices.

65

18

Living rooms.

70

22

Bathrooms

80

38

Drying rooms and trade purposes.

90

66

100

|

115

Glass-Houses

Temperature required when it is 300 outside.

Length of

4-inch Pipe per 1000 Feet of Space.

Purposes.

Degrees Fahr.

40

22

Cool-house for half-hardy growths.

45

Fruit, conservatories.

50

39

55

48

Grapes, tomatoes, cu-cumbers.

60

58

65

69

70

81

Orchids, melons.

80

110

Pines, and forcing.

In finding the surface required in brick - built structures the above table makes no allowance for a varying area of glass (windows), and as glass is a rapid loser some consideration should be given to this. Many engineers are satisfied to use a table such as that given, and then make a mental allowance as the size of the windows is seen, but others prefer a calculation such as the following:-

To obtain 60° in any ordinary brick-built room when it is 300 outside: allow 1 square foot of heating surface to each 5 square feet of glass, with the addition of 12 square feet of surface to each 1000 cubic feet of space. If the room has two exposed walls, add 10 per cent to the above.