We had a problem with our toilet flush mechanism. It would make an howling sound, whenever a tap in the house is opened. Also one of the taps would make a knocking (water hammering?) sound.
A technician from New Canadian Drain and Plumbing (NCDP) visited and adjusted a few shutter valves. I was not convinced that this had fixed the problem, but after the adjustment the problems went away.
A few days later, the howling sound came back. I called NCDP again and this time another technician (Mallick) visited. He took time inspecting the assembly of the toilet flush and also the shower. He removed a couple of items (jets?/stoppers?) from the shower and demonstrated they were blocked thus creating a pressure differential and thus causing the howl.
Again a few days later, the howling sound came back and with it another new problem which hadn't existed before. At this point, I had already paid close to $300 and the problem still existed and then some.
Mallick came down again and promised that he will fix the problems at no cost to me.
The toilet is from a company (Yato) whose products are not widely available in North America. The toilet came with the house and I had little interest in changing the complete toilet. So spares and general know how it work is not common knowledge in North America and also no material was available on the Internet. But Mallick somehow managed to find the useful combination of spares from local stores and made it work with the toilet.
For the shower, he had bought, water hammer reducers and fixed them. While there is little bit of hammering now, it is something that I can live. Moreover, it appears that the temperature adjustment valve is the one causing it and I might choose to fix it at a later time.
For fixing these, Mallick spent around 3-4 hours. I neither payed for his labor nor for the spares he bought. While I was initially frustrated that the problem wasn't fixed, I truly appreciate the fact that Mallick made a promise to make things good and followed through on it.