Slow flow rate?

[Jack Tucker]

Hi, I've just had a new shower put in and changed the shower head, the water coming out doesn't seem that great, although the one before wasn't much better, is there anything I can check?
I have a Worcester greenstar 28i, with I think 11.4 litres per min, is this sufficient for a powerful shower? The boiler was purchased about a year and a half ago, wondering if if should of bought a better one. I haven't tested the water coming into the house yet, will do tomorrow some time. What's the easiest way of doing this as I've read if I'm getting 6 litres for example, there's no point in having a 15 lpm boiler?

Any help will be appreciated

 

[cjard]

Go to the sink nearest the stop cock (nearest in the sense of "first tap on the pipe, after the stopcock) and turn the tap full on with a jug at the ready, fill a litre, pour it out, fill a litre, pour it out etc, for one minute.

Remember the cold supply rate to your house dictates how much water you can get out of your shower(which may be worse than the nearest tap) regardless of your boiler. If your boiler can raise 15 litres per minute by 30 degrees and you only feed it 10, then it can only raise 10 litres per minute, but to a higher temperature. Remember that your shower mixes hot and cold, so if your boiler is set to raise the temp to 60 degrees, let's say it'll only do 7.5 litres a minute at that raise (if your incoming water is just above 0) but then you'll want to mix that down to 40 for your shower, so cold is added and that is water the boiler doesn't see, supplied in parallel from the mains. The amount of hot water your boiler hence has to supply to give you a 40 degree shower is lower than the amount it can supply, but if there simply isn't enough water arriving to feed the shower, whether it passed through the boiler or not is a moot point

 

[45yearsagasman]

fill a litre, pour it out, fill a litre, pour it out etc, for one minute.

Or simply time 1 litre and do the maths.

 

[Jack Tucker]

Thank you very much for the quick response. The cold flow rate was 12.5 litres per min, hot was 8.5. Surely I should be getting 11.4 out of the hot water supply?

 

[denso13]

It depends how hot you run the water. If, like some of my family it needs to be as hot as the sun, you'll get a lot lower flow rate than if it was a bit cooler. The 11.4l/m will be for a set temperature rise.

 

[cjard]

Thank you very much for the quick response. The cold flow rate was 12.5 litres per min, hot was 8.5. Surely I should be getting 11.4 out of the hot water supply?

I'm sure I covered that part when I was talking about temperature rises:

"If your boiler can raise 15 litres per minute by 30 degrees and.... if your boiler is set to raise the temp to 60 degrees, let's say it'll only do 7.5 litres a minute at that raise"

Your 11.4 lpm is for a set change in temperature e.g. 30 degrees. If your boiler is getting water at 5 degrees C and you have it set to putput 60 deg c, that's a 55 degree rise. If it will do 11.4lpm when it only has to lift the temp 30 degrees, what do you think it will do when the lift is double? Boilers lift hotter by making the water stay "in contact" with the flame for longer. Ignoring modulation, they do this by slowing the flow down so it takes longer to pass through the heat exchanger.

 

[cjard]

fill a litre, pour it out, fill a litre, pour it out etc, for one minute.

Or simply time 1 litre and do the maths.

Easy for someone who appreciates maths, but I know plenty of people who fall at a hurdle like "If you get a litre out in 7 seconds, how many litres do you get out in a minute?"

Cue a conversation between me and an ex once:
"how far is Birmingham?"
"100 miles" I replied
"and how long will it take to get there?"
"about an hour"
"isn't that rather fast?"
"well, you tell me- how fast did I drive?"
"I don't like maths"

On the upside she was, however, incredibly attractive