I do not see a forum for plumbers, so i will ask it here in General Chat.
My guest house is on top of a hill, so the water pressure is insufficient to let a few people shower at the same time. I have installed a 5000lt tank, that gets filled from the municipal supply, from where I then pump it to the house. I have a Flow Control switch on a water pump that can deliver 5 Bar. The municipal supply link to this supply from the tank, so that when the pump is out of action for some reason, we still have minimal water pressure in the house.
The problem is that lately the pressure is climbing to just below 7 bar and cause all types of havoc, like leaks and pipes bursting. I took the pump and control to the retailer today and they say I bought an overkill pump. I said the unit is faulty, as it never went over 5 bar in the beginning and they sold it to me as the right size pump. Eventually I spoke to a gentleman on the phone, the supplier, that explained to me that the problem is that the municipal supply pressure is added to the pressure supplied by the pump. The pump can deliver 5 bar max and the flow control switch it of when the pump is delivering it's max capacity. It is not looking at the pressure in bar, but rather the flow from the pump. So this is the first thing that I misunderstood and still do not understand completely. I previously used a pressure switch that switch the pump off when a certain pressure has been reached, like 4.5 bar. They however pack up every now and then and I am tired of it's problems, so I went for something else, not understanding how it works.
The supplier then said that I must isolate the municipal supply from the house, so that it only supply the tank and therefore not contributing to the pressure to the house or back pressure to the pump. So, this is the second part that I do not understand. In my mind, the say 2 bar from the municipality can not be added to the 5 bar from the pump. I reason that the total pressure will stay 5 bar. Yet, in practice it could be true what he say, as the total pressure to the house this morning was nearly 7 bar. Can someone explain this to me? If this is true, it can be that the problem was there all the time but unnoticed, because the municipal pressure might have increased lately.
I have done what he suggested this afternoon, and the max pressure now stays at just over 5 bar. I am worried however, as my son says he tried it in the past, by turning off the municipal supply and it did not help. So I will keep an eye on things and see how it develops, but if a pro can explain what is happening, I will appreciate it.