If comparing a house as a person and plumbers as doctors, I would leave my house problem to the plumbers and entrust that they will do the best for it. But plumbers are not doctors, houses are not a human beings.
I had only small plumbing problems with choked pipes before. After changing to new better sinks, I had no plumbing problem for a very long time. I am totally a dummy about plumbing.
I called a team of plumbers to take a look. They came and quickly took a look and told me that they need to cut all the pipes connecting to my basin, show point, bath tab and build new sets of cold and hot pipes outside my bathroom wall. They asked, can you accept it? Wow, I said, how much. They told me $2500.
Not only $2500, my beautiful marble wall bathroom will have ugly pipes exposed. I immediately refused. Although I am a dummpy in terms of plumbing, I know it is ridiculous. Imaging your blood vessel is wrong somewhere, doctor wants to cut all your vessels and build new sets of them out of your body.
Someone introduced a plumber for me. He came and he said he needs to knock the wall where most probably the buried pipes are leaking. I agreed. After knocking the wall with a round hole, there exposed three pipes, the brown cold, hot copper pipes and one white PVC pipe. The plumber was very sure that the copper pipes are leaking.
But I touch the copper pipes, not wet at all. He told me that he needs to knock a bigger hole so that the copper pipes will have no wall attached. The water will be dripping down from the copper pipes. To do this, it means that the other side of my bathroom marble wall will be spoil a bit. Since the marble wall is hidden inside the basin cabinet, I agreed.
But after knocking the marble wall, the pipes still had no water dripping down. The plumber told me that, there must be a very small hole leaking on top of the pipe, we need to wait to tomorrow to feel the dripping.
But I already sensed something is not right. The bottom of the wall is very wet. There were three times, water gushing out from the bottom of the wall after taking shower. If there is small hole and dripping of water, how can water gushing out? The plumber refused to listen to all these evidences and told me that water can travel and hide somewhere.
I notice the white pipe near the copper pipe, I asked him, what the white pipe is. He told me it is linked to the water heater. My water heater is installed in the bathroom ceiling. The PVC pipe is buried in the wall. I asked if it is possible that this pipe is leaking. From the position, if this pipe is leaking, it explains very well why both sides of the corner of the wall are wet and the knocked part of the wall is highest point that is wet.
But he said that the pipe is only for steam to come out when water heater is hot. It goes to the main drain hole and will not leak.
We called off a day. The next day, we checked the copper pipes and they were still dry without any trace of water. But the most ridiculous thing is that the plumber wants to anyhow cut the copper pipes from where they are exposed and build a new set to connect to the ceiling part of the pipes as if there is leakage in the pipes along the way. I immediately stopped him and asked him to wait. He somehow accused me of not trusting him and didn't want to continue the job.
The next day, I asked another plumber to take a look. I especially asked him if there is problem with the white PVC pipe. He said, nothing is wrong with the water heater and the PVC pipe will never leak. He also said that the pipe is terminated ad the floor drain hole. He said the water will travel, the place you see water may not be the place the pipe is leaking. He needs to use some equipment to check where the leakage is. It costs $200 for him to do the check only.
I told him to wait for a while because I have strong feeling that the PVC pipe connecting to the water heater may be the problem.
I started frantically searching of information about water heater. I had never know there is a Temperature and Pressure (T & P) safety valve in the water heater. A safety device called a temperature and pressure relief (T&P or TPR) valve, is normally fitted on the top of the water heater to dump water if the temperature or pressure becomes too high. The T & P safety valve is connected to a PVC pipe which is called overflow discharge pipe. The T & P valve will open under such circumstances to let go of water to the PVC pipe to easy the pressure of the tank. Without the T & P valve, the water heater tank could possible be a steam bomb that may explode sometime.
I also understand, that the PVC overflow discharge pipe must terminated 6" above the floor level and cannot be at a drain hole. The reason is that when hot water comes out, it need to be flush out quickly and cannot be too close to the floor level. Also if siphoning occurs, the liquid (be it dirty water, household chemicals, oil, etc.) will be drawn back into the water heater tank, thereby contaminating the household drinking water supply. If PVC discharge pipe terminate at the drain hole, if your drain hole is choked and full with dirty water, your water heater tank will be contaminated.
I can image how the PVC pipe terminate in the wall now. It is not at the bottom of the wall, but 6" high above floor. This explains well the highest point where the wall is wet is near the PVC termination point.
This also explains why sometime there is gushing of water because overflow discharge from water heater can be very strong sometime.
I believe the water heater has problem. The water heater is Ariston brand and people advise that the new Ariston water heater normally has shelf life of 5 years. I made a decision to replace the water heater to a new one.
But I still need to make 100% sure the problem is due to water heater. I turned off the water heater for a few days. The walls were no longer wet.
I immediately called one water heater store recommended in a forum and they changed the water heater for $375. $245 for a Joven 30L water heater and $130 installation.
The problem is solved with total cost of $575. I paid the plumber who knocked the wall $200,
The whole fiasco is now finally over. The lesson I learned is that you need to find a good plumber. If you cannot find one, you need to be one yourself.