SMOKE TEST No 1 There had been a complaint of rats in the lower part of the Ormeau Road area in Belfast and it was laid squarely at the door of the Sewerage Section. Sam, a plumber, was sent to investigate and decided that he needed a smoke test.
I have always found it strange that smoke really does issue from a sewer up through the earth and travels quite long distances through cracks in pipes and the ground. This feature of smoke was used to assess whether a sewer pipe had been breached or was leaking. Something much more scientific is used today.
Theoretically every pipe leading to a sewer is trapped with a water trap, so there should be no risk of smoke entering a house. To carry out the test the operator closes the end of the pipe, or puts a temporary block at some point. At the other end he attaches a box, which is really only a source of smoke, and the bellows will force it through the pipe. He puts a rag, heavily impregnated with oil, inside the box, lights it, and then, using the bellows, pumps the smoke into the pipe until it is seen issuing out through a small hole in the block at the far end. If it issues from nowhere else it is assumed that the pipe is tight and has no leaks.
In Sam’s case this was not quite what happened. In the first instance someone shouted that smoke was issuing from the lamp standards, and as these were gas lamps panic ensued until he managed to explain what was happening. Next he heard screams coming from the back-yard of one of the houses. The sewer in question ran between the backs of two rows of houses and at that time, those houses only had outside toilets in the yard. Apparently a householder had been in one when she found smoke, firstly coming up round her feet, and then all round her; her plight was understandable. Finally he had to pacify the fire brigade who had been called with a 999 call from someone further- afield who had found smoke coming up through the floor boards.
The theory that the sewer was at fault, seemed to be thoroughly confirmed.
SMOKE TEST NO 2This test took place on a Saturday morning when I was working for the contractor. The sewer we were laying was in running sand, a very unstable material and we did not want the trench lying open over the weekend as the results of a possible slip could have been dangerous and expensive, added to which if a smoke test failed then we might have had to carry out a water test which can take hours.
We were dealing with a very fussy Clerk of Works who liked his authority and enjoyed wielding it. He knew as well as we did that there was nothing wrong with the pipe, he had seen every joint made, but the book said smoke test before passing the work, so smoke test we did. We set it up, put in the disk at the end of the pipe with the one-inch hole to show the smoke had gone the whole way through the pipe, and then tea was up. Well it was up for the Clerk of Works, it was up for the men, but not for the foreman and not for me, we were pumping the smoke for all we were worth and it was not reaching the other end. The Foreman said to me, “You go and join the Clerk of Works and I’ll have it fixed in the mean time, no sense both of us being here.” I followed his advice.
About ten minutes later he stuck his head into the hut and said all was ready for testing and when the Clerk of Works and I went to the other end, there , sure enough, there was the smoke puffing out in spurts in time with the pumping of the man at the other end. Honour had been satisfied and come twelve o’clock we would all be going home.
When I was out of earshot of the Clerk of Works I said to the foreman that I was surprised at the amount of smoke issuing, considering the length of the pipe, usually there is dilution by the air within the pipe for some time, and it seemed to me the smoke was denser than I would have expected.
He smiled. “I helped it on a bit,” he said. ” I thought it could do with another smoking rag so I put it in the other end, I knew he’d never guess, he’s all talk and no experience.”
This accounted for what I had seen. The foreman, unknown to me and the Clerk of Works had inserted a piece of burning rag at the other end of the pipe from the bellows and the air within the pipe was being pushed by the bellows to make the smoke from the second rag issue from the small hole. Instead of the pipe being full of smoke as it seemed, it was probably partly full of air.
For all of ten seconds I wondered what to do, and then for another ten seconds I suppressed my conscience with the thought that, firstly, knew the pipe was secure, and, secondly, I saw the Clerk of Works from time to time, I saw the foreman daily.