be bedded thereon, and dished out for the hand to pass round under the joints of the drain-pipes. Stakes could be driven down in the bottom of the trench at intervals of 6 or 12 ft. to mark the height at which the concrete is to be filled up, and wood templets employed for forming the dishings for the joints.

12. The drain from point to point-manhole to manhole -should be laid true in line and section, and the joints of the drain-pipes should be carefully and soundly made with Portland cement, so that the joint is of equal thickness all round, the underneath portion being well tucked into the socket with the fingers, care being taken that none of the jointing material is left projecting inside the pipes. The cement should be highly faced off round the joint at about an angle of 45°.

13. After the drain has been laid it should be allowed to stand for about 24 hours, when it should be filled with water and tested. A little of the water will be absorbed by the cement and also by the drain-pipes, but this can readily be allowed for. Practically the drain should be required to hold water like a bottle. The drain having been thus tested and found to be sound, flaunch off the sides of the drain with Portland cement concrete; or, if preferred, cover over the upper part of the drain, and encase it with concrete to the depth of 3, 4, or 6 in., as circumstance may dictate. And if the drain is inside the house, test it again.

14. No right-angled junctions, bends, or elbows should be used, and where inspection-chambers are not built so that channel-pipes could be fixed and adjusted to suit the requirements, the junctions should be tilted a little, to prevent back-wash up the branches. Special channel-pipes and junctions are now made by most pipe manufacturers.

15. I confess that I often come across a lot of money sunk in building manholes which I think could be better employed than in affording means of access to a drain which

may never be used. For the drainage of my own house, provided I knew the work would be well and efficiently carried out, I should be quite content to have just one or two inspection-chambers in the whole system. But for examining and for testing drains manholes are of great value.

16. For soil-drains inside a house, and for all places where any leakage from a drain would soak into or under a house, I prefer cast-iron pipe, of the heavy underground water-main strength, i.e., for a 5 in. drain, and under that size, the pipe in its thinnest part should be in. thick; and for 6 in. and 7 in. drains the pipe should not be less than in. The pipe should be coated with solution (Chap. XXVII., Art. 7), and each pipe should be tested before it is fixed by ringing it with a sounding blow from a hammer. (Chap. XXVII., Art. 8.)

16.

The joints should be carefully caulked with a ring or two of spun yarn, and the remaining space filled up with molten lead (soft pig lead) and caulked in, the depth of the lead being not less than 2 in., but 2 in. is better (see fig. 110).

As already explained (Art. 6), I prefer iron drains to be carried upon brick piers, or strongly secured to the face of a basement wall, or the wall of a subway. At any rate, no iron drain should be allowed to come into contact with lime; and where an iron drain is laid in a trench, and it is not carried upon piers with a granolithic or stone bed hollowed out to receive the drain (two to a 9 ft. length), and is laid upon a concrete bed, the concrete should be made with Portland cement.

17. Although the size of a drain is now much more considered than was the case some years ago, the drain is often of much larger size than necessary. A 6 in. drain is large enough for ninety per cent. of the houses in London, and a 5 in. drain would be quite sufficient for scores of cases where even to-day 6 in. drains are being fixed.

18. I have a great objection to access-chambers to drains inside a house, either manholes to stoneware drains or sight-holes to iron drains, for in my examinations I have often found that the covers and means of access have not been made absolutely air-tight; that jobbing men, in their examination of a drain, have not always been careful enough to replace the manhole covers or sight-hole covers as they found them. But where no access is provided, some half-fledged sanitarian, when he happens to be called in, throws up his hands in wonderment, and frightens the poor householder into an order to fix sight-hole pipes or inspection chambers "immediately."

In fig. 163 is shown a heavy cast-iron sight-hole pipe, for

fixing to an iron drain by caulked lead joints, and with strong gun-metal bolts for securing the cover, B, to the pipe.

DRAIN-FLUSHING.

19. It is now the good custom to fix at the head of the main drain (and in some cases at the head of every important branch drain) an automatic flushing-tank for cleansing the drain, by passing a scouring flush of water through it every 24 hours. Instead of fixing such tanks for discharging about 150 gallons of water at a time, as some authorities arrange, I prefer flushes of less than half that quantity, and in many cases I should prefer 40 or

50 gallons of water discharged every 12 hours, to 80, 150, or 200 gallons discharged once in every 24 hours. With the larger flushes there is often great danger of syphonage. I have known the water-seals of several drain-traps-intercepting-traps to sinks and lavatories, etc.-syphoned out by such discharges: and more than that; in one case, where a great engineer had been concerned in planning the drainage, the automatic flushing-tank discharged such an enormous body of water that fæces and other matters were back-washed up through many of the surface-traps, and the water-seals of closet-traps syphoned out.

CHAPTER XXXIX.

HOUSE-DRAINS (continued).

DISCONNECTION AND VENTILATION.

1.

HE value of disconnection is now so generally underof is now words dig us the

THE

necessity of trapping off sewers and cesspools, and aerating the drains.

We are now so near to the closing cover of this little book, that there is no space left to discuss the many disconnecting-traps now in use.

2. Unfortunately several vestry boards still insist upon that obstructional appliance the valve-flap. This flap they require to be fixed upon the end of the drain inside the sewer. Where a flap-valve is insisted upon, the last length of drain-pipe into the sewer should have a sharp fall, even if it entailed less fall in the other part of the drain.

3. Although the manhole drain-syphon, fig. 164, has been superannuated for some years, it is still being used here and there where the light of sanitation has not yet dawned. When such traps are examined, after they have been in use only a short while, they are found to contain pailfuls of filth.

B

Fig. 164.-SECTION OF A MANHOLE DRAIN-SYPHON.

In measuring the quantity of water held by a 6 in. manhole drain-syphon, as fig. 164, I have found it to hold more than twice the quantity of water held by my patent disconnecting-traps, figs. 165, 167, 170, and 174. A 6 in. man

Fig. 165.-SECTION OF A 6 IN. VENTILATING DRAIN-SYPHON.

hole drain-syphon, as fig. 164, holds generally more than two gallons of water. How is it possible to change the contents of such a trap with the flush of water allowed for closets, viz., two gallons? The fact is, such traps are