Water pressure tank and legionaries

chillit

My house is currently being re plumbed and I am looking for some advice regarding an internal pressure tank.

The new system is planned to run off the pressure of the well pump. I was planning to have no cold water tanks at all in the house as I have seen a few houses setup this way. The plumber however is suggesting to include a small pressure balancing cold tank of about 50 litres in the hot press. He says that without this if you are showering upstairs and someone turns on the tap downstairs then the shower pressure will drop.

My understanding is that the water in this balancing tank will only be used sporadically to balance the pressure thus meaning that it is largely stagnant.

Because the tank is inside the insulation later of the house the temp in the hot press is likely to be around 20-22c which is the temp that legionella starts to multiply at. Does anyone know if this is a safe approach. I.e. putting a stagnant cold water tank it a 20-22c hot press.

The alternative suggested by the plumbing is to put the pressure balancing tank in the pump house but this will then require 2 supply pipes to come into the house. This was just an alternative suggestion when I brought up the legionaires risk.

All thoughts or ideas welcome. The plumber says that he always those this setuo and no engineer has ever commented about it being a problem. My engineer also seemed a bit nonplussed when I mentioned it so perhaps I am worrying about nothing.

BryanF

What type of Heating system is planned?
How much pipework will be susceptible to ~20deg temps?
Is there anyway to heat this water once a week to above 60degs?

chillit

Central heating and hot water heating is via oil boiler and wood burning stove. We expect more use of the wood burning stove due to a ready supply of wood.

The hot water tank will have 3 coils. One for the boiler, one for the stove and a reserve for possible solar in the future.

My understanding is that this balancing tank is a cold water tank connected only to cold water pipes so I don't think it is suitable to heat to 60 degrees at any stage.

The house is very well insulated with a high thermal mass so I sort of expect that everything inside the insulation layer will be at 20-22 degrees most of the time. That would include the water pipes I suppose.

Saying that all the pipes are insulated so I suppose this would keep the cold water pipes somewhat below the ambiant air or room temp.

I think this pressure issue must effect all 2 storey houses so a common approach must be out there surely.

BryanF

Perhaps this would be better in the plumbing forum ?

K.Flyer

Is this a 50 litre "expansion vessel" you are talking about?

chillit

@flyer No there is already an expansion tank attached just after the well pump. This seems to be and additional tank with a booster pump on it.

K.Flyer

So would the layout be...

From Well pump ==> direct to Water tank ==> to Pump ==> then To Hot Water Cylinder and Cold Water taps etc?

Calahonda52

op re this
My understanding is that the water in this balancing tank will only be used sporadically to balance the pressure thus meaning that it is largely stagnant.

This suggests that the pipe from the pump is tee'd at this tank and that the tank takes up the slack if demand is too high/ stop pump rapid cycling maybe also.

However my understanding of these setups is that there is no Tee, but that the water passes through this tank and so is always refreshed as it provides water to the cold and also the hot.

Maybe sketch a pipework diagram schematic and post it