Impact on water pressure with a shower head/Tap combo

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Hello, Does anyone have any info or advice on if/how much of an effect having one of the bath tap set ups that comes with a built in shower head attachment will have on the overall pressure?

I have previously been advised that my current boiler might struggle with pressure and maintaining heat when I have a bath installed in my upstairs bathroom, I have a Worcester Greenstar 24i Junior boiler running currently 8 rads and boiler is downstairs but bathroom is upstairs,

Any advice will be greatly appreciated
 
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1. It will have no effect on the pressure. It might have an effect on the flow rate.
2. Combi boilers can heat either hot water or central heating, but not both at the same time. When hot water is called for by turning on a hot tap, the boiler diverts its heat output to heating hot water.
3. Provided that:
3.1 The incoming cold mains pressure is around 1.5 bar AND
3.2 The incoming cold mains flow rate of around 15 to 20 litres per minute AND
3.3 The bathroom is no more than 1 storey above the floor where the mains comes in THEN
3.4 You should have no problems.
4. Note that a combi such as yours is unlikely to support two hot outlets being open at the same time without a loss of hot water performance being perceived at one or both outlets.
5. If you want a definitive answer you would have to know the pressures and flow rates noted at 3.1 and 3.2 above.
 
1. It will have no effect on the pressure. It might have an effect on the flow rate.
2. Combi boilers can heat either hot water or central heating, but not both at the same time. When hot water is called for by turning on a hot tap, the boiler diverts its heat output to heating hot water.
3. Provided that:
3.1 The incoming cold mains pressure is around 1.5 bar AND
3.2 The incoming cold mains flow rate of around 15 to 20 litres per minute AND
3.3 The bathroom is no more than 1 storey above the floor where the mains comes in THEN
3.4 You should have no problems.
4. Note that a combi such as yours is unlikely to support two hot outlets being open at the same time without a loss of hot water performance being perceived at one or both outlets.
5. If you want a definitive answer you would have to know the pressures and flow rates noted at 3.1 and 3.2 above.
That is some detailed answer, thank you for that really appreciate it,
Where you refer to two hot water outlets I take it you mean central heating (rads) as one and then running hot water as the second yeah? If that is the case what could be done to change (or pick) just one output at a time when needed, I would think maybe a thermostat yeah?

Also is there an easy way to find out the pressure and flow rates with my boiler that I would be able to get myself (sorry if that sounds a silly question but I’m clueless with all this)
 
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1. No. Two outlets = say one shower and the kitchen sink hot tap.
2. Flow rate can be easily measured. Mains cold supply (outside tap, kitchen sink cold) opened into a bucket, time how many seconds it takes to reach the 10 litre mark. Then litres / minute = ((seconds / 60) x 10) . However, you need to be sure there are no restrictions (such as isolation valves (other then full bore ones) or narrow flexi hoses between source and outlet. Outside tap is usually better as has no flexi hoses.
3. Pressure needs a pressure gauge such as Screwfix item 82412. Measure as:
3.1 Static pressure = gauge attached to one mains cold water outlet, no other cold mains outlets open.
3.2 Dynamic pressure = gauge attached to one mains cold water outlet, at least one other cold mains outlets open. E.g. gauge attached to outside tap point, kitchen cold tap running.
 
1. No. Two outlets = say one shower and the kitchen sink hot tap.
2. Flow rate can be easily measured. Mains cold supply (outside tap, kitchen sink cold) opened into a bucket, time how many seconds it takes to reach the 10 litre mark. Then litres / minute = ((seconds / 60) x 10) . However, you need to be sure there are no restrictions (such as isolation valves (other then full bore ones) or narrow flexi hoses between source and outlet. Outside tap is usually better as has no flexi hoses.
3. Pressure needs a pressure gauge such as Screwfix item 82412. Measure as:
3.1 Static pressure = gauge attached to one mains cold water outlet, no other cold mains outlets open.
3.2 Dynamic pressure = gauge attached to one mains cold water outlet, at least one other cold mains outlets open. E.g. gauge attached to outside tap point, kitchen cold tap running.
Again thank you for such a detailed response, realistically then if running a bath/using the shower head attachment as long as there are no other taps running then pressure should be ok?
 
Usually the bath would need to be filled slowly. Depending on the flow/pressure with the hot tap fully open the combi may not be able to heat the hot water up hot enough, so it'll mean only opening the tap say 1/2 or 3/4's open to get the water hot enough. It will take a while to fill the bath - 20 odd mins is a good gauge to start with.
 

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