Hello,
Just had a new combi boiler installed, converted from an old system boiler with hot water tank and cold water storage in loft.
When I run the hot water tap in the bath it's quite slow, I guess this is to be expected after reading about it. However, when I turn the cold tap on the hot water goes even slower. So running a bath is going to be a pain. In addition to this, when running the HW in the bath the flow for the HW in the bathroom sink is really really slow.
My question - Is this to be expected? It doesn't seem right but I've never owned a combi before. The boiler display says the flow is 11.5L but it's definitely not that at the taps.
Are you a tradesperson and able to answer this question?
There could be an issue with the cold water main giving the correct volume of water, the 11.5l flow rate that you refer to is important but so is the flow rate at temperature rise. Some manufacturers state flow rate at 40 degree temp rise, some state 35 degrees which isn’t as good and some state as low as 25 degree. I’d start by checking flow rate and temperature rise against manufacturers data.
Hi, it is always an essential requirement to test the mains pressure and flow rate before converting the system to combination boiler as it won’t work if the existing pressure is lower than 1.5 bar which is the minimum pressure any combi boiler needs to provide hot water at a sufficient temperature rise (normally around 35-40 degrees). The combi boiler doesn’t slow down the water pressure coming into the boiler however if it’s already low pressure then the hot water coming out of the boiler will be nearly the same pressure.
The solution is to upgrade the incoming Mains from the street to the property stop valve in bigger pipe size but if it’s not possible due to cost then the cheaper option would be installing a special Mains improvement pump which is designed for combi boilers with low Water pressure.
Thank you
Amar Kindi
Hi
There are many factors to consider, mains incoming supply, restrictions with in the pipework in the house i.e length of pipework, elbows, valves, taps e.t.c. An average bath will take about 120/140 litres of water, taking about 10/12 minutes to fill at 11.5l/min.
in adequate pressure and volume from incoming main,they have used old hot and cold pipework (usually 22mm in old systems )this will lead to pressure drop,this is a common problem with combi boilers.
