B
Bernie2
Another bit of info that might be helpful to new Plumbers are some observations about water FLOW.
In the UK, water fixtures usually have a minimum water flow rate that is required to be met for them to work properly.
Some of the most obvious are the combi boiler and the shower. Both of which usually have minimum flow rates for them to work.
A typical combi requires between 2-3 litres per minute before the burner will even operate. Obviously this can cause problems if you are using low flow equipment, you simply don’t require to draw off enough hot water for the burner to kick in.
That is why, before installing, site requirements have to be checked and met.
It’s roughly the same with a shower most of us seem to like a flow rate of about 6 litres per minute. But with low flow shower heads coming onto the market and the overall reduction of water use set to become part of the Building Regs, can we be sure we will always have the luxury of being able to have a 6 litre shower.
Funnily enough there is no upper flow limit for showers, while the US states 9.5 litres as the maximum.
Measuring the flow rates of a fixture is easy enough when it’s fitted and working, all you need is a measuring jug and a stopwatch. Then turn the tap on full and time the water coming out and how much of it there is. That gives you flow rate per minute, or second, or whatever time you want.
But lets be honest, it’s the flow rate you want to know before you pipe the fixture up not after it’s working, to ensure you meet the minimum requirements for the fixture.
Its pointless piping it up and then a day or so later an angry customer comes on the blower “I am not getting enough water coming out, it takes ages to fill.”
Fortunately we get away with this a lot, because most UK domestic water supplies both hot and cold now come off the water mains. And the main is a decent supply. Yet who has never had complaints of poor flow from a combi?
The minimum flow rate for most UK fixtures can be found in various places including BS 6700:2006.
But flow rates are expected to be tightened up, when and if the new guidelines given in Building Regs G 2009 requiring people to reduce water use to 125 litres per person per day come into use.
Its simple really, we have high mains pressure so high flow rates, and when we open a tap we usually loose more down the plughole than we use.
I suppose it may come down to imposing fines, or at least charging extra per litre for over use of water above 125 litres, using your water meter records as proof of excess.
Don’t forget petrol, was once thought dear when they sold it by the gallon, but looked a lot cheaper when they started to sell it by the litre. In reality of course it was all smoke and mirrors, it was just as dear by the litre as it was by the gallon.
So don’t forget once all water is on a meter, then they can charge you per litre, adjusting your use through price. It’s a nifty idea, you don’t have to ask people to turn taps off, just charge them more and they will probably turn them off without having to ask them.
So nobody is going to be to happy if their taps let 20% of their daily allowance go down the plughole, just because the flow rates where too high and they never left the plug in the bowl to catch the water.
Let’s be honest, we probably tend to rinse our hands under the running tap rather than fill the bowl and wash. That must use loads of water.
Anyway that is a bit of a taster about flow and how we will probably all have to become more aware of our water use in the future.
Some even say, that they may consider changing tap tails from 15mm to 8mm to help reduce the flow and of course downsizing our pipe sizes.
Now how do you know what size pipes to install to get the flows you want?
Well working a flow rate out by taking into account all the variables involved such as pressure, velocity, resistance, viscosity, rate of use, temperature and so on is quite involved but fortunately there are some easier ways.
I would recommend having a look at the “uk copperboard.co.uk” “Pipe sizing for hot and cold water Parts 1 and 2. It’s a good write up.
Also consider having a look at Tommy Box’s theory.
Okay so it might fry your brains a bit when your busy, that is why planning time should be included in your price.
Also there are plenty of charts and free software about that will do most of it for you.
The Charted Institute of Plumbing and Engineering put out a piece called Useful Info, which has a copy of Thomas Box formula on it.
Sorry I an unable to put equations on myself, I simply don’t know how to put them in a forum mail.
But anyway it’s better to get them from a place of some authority than say “a guy on the internet told me”. It’s just in case you need to provide proof of authenticity. And saying its from the recognised UK copper board, CIPE, Building Regs, British Standards or anywhere with recognised standards that people know, would seem better, and more professional than saying “off some bloke on the internet” as right or wrong as they may be in wanting to help. The Internet is good for first step info and giving pointers, but at some time you may need to state recognised sources especially if your getting sued for what somebody may regard as a cock up.
Lets be honest if you never did the gas tightness test after a gas repair, nobody is going to listen if you say
“Well Fred told me it would be okay, and he has been a gas engineer for 200 years!”
No! What would probably happen is that you would get hit over the head with the gas regs.
But if it said it was okay in the Gas Regs, and you could show them where it did, you could probably stand up as innocent or at least share the blame with the Gas Regs.
Anyway I feel sure the lads can add loads more than I can to this thread. So I will leave it there.
In the UK, water fixtures usually have a minimum water flow rate that is required to be met for them to work properly.
Some of the most obvious are the combi boiler and the shower. Both of which usually have minimum flow rates for them to work.
A typical combi requires between 2-3 litres per minute before the burner will even operate. Obviously this can cause problems if you are using low flow equipment, you simply don’t require to draw off enough hot water for the burner to kick in.
That is why, before installing, site requirements have to be checked and met.
It’s roughly the same with a shower most of us seem to like a flow rate of about 6 litres per minute. But with low flow shower heads coming onto the market and the overall reduction of water use set to become part of the Building Regs, can we be sure we will always have the luxury of being able to have a 6 litre shower.
Funnily enough there is no upper flow limit for showers, while the US states 9.5 litres as the maximum.
Measuring the flow rates of a fixture is easy enough when it’s fitted and working, all you need is a measuring jug and a stopwatch. Then turn the tap on full and time the water coming out and how much of it there is. That gives you flow rate per minute, or second, or whatever time you want.
But lets be honest, it’s the flow rate you want to know before you pipe the fixture up not after it’s working, to ensure you meet the minimum requirements for the fixture.
Its pointless piping it up and then a day or so later an angry customer comes on the blower “I am not getting enough water coming out, it takes ages to fill.”
Fortunately we get away with this a lot, because most UK domestic water supplies both hot and cold now come off the water mains. And the main is a decent supply. Yet who has never had complaints of poor flow from a combi?
The minimum flow rate for most UK fixtures can be found in various places including BS 6700:2006.
But flow rates are expected to be tightened up, when and if the new guidelines given in Building Regs G 2009 requiring people to reduce water use to 125 litres per person per day come into use.
Its simple really, we have high mains pressure so high flow rates, and when we open a tap we usually loose more down the plughole than we use.
I suppose it may come down to imposing fines, or at least charging extra per litre for over use of water above 125 litres, using your water meter records as proof of excess.
Don’t forget petrol, was once thought dear when they sold it by the gallon, but looked a lot cheaper when they started to sell it by the litre. In reality of course it was all smoke and mirrors, it was just as dear by the litre as it was by the gallon.
So don’t forget once all water is on a meter, then they can charge you per litre, adjusting your use through price. It’s a nifty idea, you don’t have to ask people to turn taps off, just charge them more and they will probably turn them off without having to ask them.
So nobody is going to be to happy if their taps let 20% of their daily allowance go down the plughole, just because the flow rates where too high and they never left the plug in the bowl to catch the water.
Let’s be honest, we probably tend to rinse our hands under the running tap rather than fill the bowl and wash. That must use loads of water.
Anyway that is a bit of a taster about flow and how we will probably all have to become more aware of our water use in the future.
Some even say, that they may consider changing tap tails from 15mm to 8mm to help reduce the flow and of course downsizing our pipe sizes.
Now how do you know what size pipes to install to get the flows you want?
Well working a flow rate out by taking into account all the variables involved such as pressure, velocity, resistance, viscosity, rate of use, temperature and so on is quite involved but fortunately there are some easier ways.
I would recommend having a look at the “uk copperboard.co.uk” “Pipe sizing for hot and cold water Parts 1 and 2. It’s a good write up.
Also consider having a look at Tommy Box’s theory.
Okay so it might fry your brains a bit when your busy, that is why planning time should be included in your price.
Also there are plenty of charts and free software about that will do most of it for you.
The Charted Institute of Plumbing and Engineering put out a piece called Useful Info, which has a copy of Thomas Box formula on it.
Sorry I an unable to put equations on myself, I simply don’t know how to put them in a forum mail.
But anyway it’s better to get them from a place of some authority than say “a guy on the internet told me”. It’s just in case you need to provide proof of authenticity. And saying its from the recognised UK copper board, CIPE, Building Regs, British Standards or anywhere with recognised standards that people know, would seem better, and more professional than saying “off some bloke on the internet” as right or wrong as they may be in wanting to help. The Internet is good for first step info and giving pointers, but at some time you may need to state recognised sources especially if your getting sued for what somebody may regard as a cock up.
Lets be honest if you never did the gas tightness test after a gas repair, nobody is going to listen if you say
“Well Fred told me it would be okay, and he has been a gas engineer for 200 years!”
No! What would probably happen is that you would get hit over the head with the gas regs.
But if it said it was okay in the Gas Regs, and you could show them where it did, you could probably stand up as innocent or at least share the blame with the Gas Regs.
Anyway I feel sure the lads can add loads more than I can to this thread. So I will leave it there.
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