Routing of hot water

[mark12345]

Hi.

Just had a british gas engineer round as our combi boiler packed up. It's working again now but while he was round we asked him about our hot water problem.

We can't get adequate hot water from the bath tap. We have to use our shower to fill the bath. ( the shower is a thermostatic mixer).

The british gas man told us that whenever we turn on a tap, the hot water always goes through the shower first, even when we turn on the downstairs sink tap which is 2 meters away from the boiler.

He mentioned the use of isolation valves.

How can I make sure the hot water is routed correctly and doesn't go to the shower first?

Any help is much appreciated.

Cheers

Mark

 

[Puddle]

Maybe two things

First is flow rate, often, especially this time of year when water coming into property is very cold. people complain hot ok through all taps apart from bath, this is usually caused by to much flow rate through bath tap, if system converted, pipework in bigger, to rectify this when using bath tap do not open fully, as you decrease flow, the water temperature will increase, you can also restrict flow at boiler, only problem with this is if customer does not know how to increase again then in summer when you could have better flow rate you are suck with lower one
The other possible problem is that you are getting a bit of back flow through the cold supply to the shower, into the hot when you run the bath tap; this can be sorted by repairing or fitting a new non return valve on hot supply to shower

 

[mark12345]

Thanks for your help.

Even when the bath tap is just open, the hot water is not sufficient. Even in the summer it's only just hot enough.

My shower doesn't have a non return valve. So I just need to fit one to the hot pipe feeding the shower.

Thanks again for your help.

Mark

Also meant to ask why the hot water goes via my upstairs shower when the downstairs tap is turned on? Can't get my head around it

Is the engineer right? I'm guessing that fitting a non return valve by my shower won't solve this problem.

Any help is appreciated

Mark

 

[radswilldo]

Are you saying the hot water circuit is run arse backwards. Dont know what to believe. Would really need to see this,call an independent plumber to inspect.

 

[Blackcatgas]

Thanks for your help.

Even when the bath tap is just open, the hot water is not sufficient. Even in the summer it's only just hot enough.

My shower doesn't have a non return valve. So I just need to fit one to the hot pipe feeding the shower.

Thanks again for your help.

Mark

Also meant to ask why the hot water goes via my upstairs shower when the downstairs tap is turned on? Can't get my head around it

Is the engineer right? I'm guessing that fitting a non return valve by my shower won't solve this problem.

Any help is appreciated

Mark

Hi Mark, either the Bg engineer has been smoking crack or youve listened to what hes said and then got your arse mixed up with your elbow, the hot water will not come from your boiler via your shower to your hot tap on the bath.
Turn on the bath tap fully, then turn it down so the flow is restricted by 2 3rds,.
the hot water tap on the bath will be 3/4" with a 22mm pipe feeding it, this is fine for when it was supplied from a cylinder but wont restrict the water enough so that your old/and or low KW combi boiler with a scaled up hw heat exchanger can heat it enough.

Iam just guessing the last bit about the combi boiler btw.

 

[mark12345]

Thanks for your reply Black Cat.

I was at work when the Bgas man came round so I'm just relaying what my wife said!!!

Our combi boiler is only 3 years old. It's a vokera syntesi 29e which is an A rated boiler which I was assured by the installer would be sufficient for my 3 bed semi.

How can I can adequate hot water from the bath tap. (the hot tap in the upstairs sink isn't that hot either!)?

PS All of the pipework upstairs is 15mm. Not sure of the pipework downstairs.

Very confused

Thanks

Mark

 

[Bernie2]

Although I can't make head nor tale of how its piped out.

The boiler you have is supposed to deliver hot water at 11.8 litres per minute. Which is quite good for a combi.

However, as usual, its not all that simple. The water companies are only obliged to supply you with 1 bar pressure at 9 litres flow and that is at the boundary stopcock to your house. Your boiler can take up to 6 bar maximum pressure on the hot water.

If, 1 bar 9 liters per minutes is all the pressure and flow you have got, then that is all you will get out of the combi. An that has to be split between the hot and the cold.

In reality taking off resistance factors it would probably be less than this.

The boiler manufacturers know this, so say the minimum pressure required for your boiler is only 0.15 bar with a minimum flow rate of 2 litres per minute.

So if your incoming mains pressure and flow are low then that could be all the pressure and flow you get.

I am afraid 2 litres per minute flow is very minimal.

A bath usually requires a lot more as does a washbasin a bit more to give what could be called a reasonable flow that feels acceptable. To give you some idea of flow rates: Water Supply 1999 flow rates

Washbasin = Designed for 9 litre per minute, min 6 l/p/m

Bath = Design 18, min 12 l/p/m

Shower = Design12, min 6 l/p/m

Sink = Design12, min 6 l/p/m

Dish washer = 9 & 6

Washing machine = 12 & 9,

You can work out your flow rate according to what you use and then compare it with the combi's

To get a rough idea of the minimum it should fill a 4.5 litre bucket in about 30 seconds.

You can't because of local and domestic conditions say exactly what pressure and flow each house has, and then it will vary depending on local demand for water.

So turning on any tap in a mains fed house affects the water flow in all the other taps.

But if the boiler was working okay when it was installed, it could be lime scale or a boiler problem.

Hope this is of some help.