Home plumbing question.

LadyInBed said:
There's nothing wrong with this question, it could easily have been framed as reducing flow rate of mains water coming into boat!
At least the question is different to the hundreds of identical questions often posted.
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Mains water coming into a boat? Now that's certainly something to ponder. :unsure:

As to whether the post is in the correct forum ..... if someone had bothered to report it the Mods would almost certainly moved it. They won't now, of course.

Richard
 
It should be a flow rate of 12 litres/minute, not per hour. What you need is a flow reducer. At its most crude you just turn down the house stop cock. You can use a simple isolator partly closed on the cold water inlet pipe to the combi. It's simple and its cheap and they are not on off. Just try and buy a decent quality unit (pegler) as the cheap ones always leak sooner rather than later. You could use a gate valve, but again cheap ones stick and snap and decent ones at quite pricey by comparison. In that respect it is similar to boats as you would not knowingly use cheap skin fittings.
 
What users does the OP have on his combi boiler to get excessive flow through it?
Unless the inlet pressure is above the 3 or 4 bar boiler manufacturers tend to specify, I'd expect the flow from say a shower ( counting the hot side only) and e.g. a kitchen mixer tap to be within the capabilities of the boiler?
Why is it a problem if the flow into say the bath is 14l/min instead of 12?

Personally I'd start by checking the pressure. Does it vary through the day?
Because if you throttle the flow to cure some perceived problem at a time of high pressure, you'll be regretting it the moment the pressure drops.
So, a pressure regulating valve is a good call, which may be why so many houses have them these days.....
The choice is whether to regulate all, none or some of the cold side. My house, the whole cold side is regulated by a whole house pressure reg valve. Which means my hosepipe is a bit weedy, but as we're on a water meter I'll live with that.
 
Alfie168 said:
It should be a flow rate of 12 litres/minute, not per hour. What you need is a flow reducer. At its most crude you just turn down the house stop cock. You can use a simple isolator partly closed on the cold water inlet pipe to the combi. It's simple and its cheap and they are not on off. Just try and buy a decent quality unit (pegler) as the cheap ones always leak sooner rather than later. You could use a gate valve, but again cheap ones stick and snap and decent ones at quite pricey by comparison. In that respect it is similar to boats as you would not knowingly use cheap skin fittings.
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As I said earlier, it's difficult to regulate flow accurately with a gate valve. Have a look at the flow curve and you'll find most of the regulation occurs in the last quarter.
 
lw395 said:
The choice is whether to regulate all, none or some of the cold side. My house, the whole cold side is regulated by a whole house pressure reg valve. Which means my hosepipe is a bit weedy, but as we're on a water meter I'll live with that.
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My entire house is also regulated by a variable PRV on the mains feed. However, I teed off the garden tap just before the regulator.

Richard
 
I prefer to post here as threads in the lounge seem to have various types of trolls that need filtering out. I'm sorry for the mistake, of course I meant 12ltr/min. The reason I want to get it down to 12 is that at present it cannot heat the water when filling the bath or sink. the shower is fine.
As said before, I plan to fit both and see which is best, flow or pressure regulation.
Again, many thanks for all the help.
Allan
 
ghostlymoron said:
As I said earlier, it's difficult to regulate flow accurately with a gate valve. Have a look at the flow curve and you'll find most of the regulation occurs in the last quarter.
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Well turn it down to there then, but most people just use a ball isolator slightly closed. Oddly enough, its cheap and with a bit of experimentation to find the sweet spot, it works. Worcester Bosch boilers have built in flow reducers and they are rubbish. The plastic capsule that contains them actually dissolves after about five or six years causing a leak They have never even attempted to improve the quality of the plastic and they have been using them since about 2004. Instead they installed a green rubbery cover for the diverter motor that would otherwise get dripped on and short circuit. Nobody understands why Worcester Bosch produce such poor plastic components...its not just the flow reducer that fails.
 
Allan said:
I prefer to post here as threads in the lounge seem to have various types of trolls that need filtering out. I'm sorry for the mistake, of course I meant 12ltr/min. The reason I want to get it down to 12 is that at present it cannot heat the water when filling the bath or sink. the shower is fine.
As said before, I plan to fit both and see which is best, flow or pressure regulation.
Again, many thanks for all the help.
Allan
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Be kind to Trolls.....
The answer with baths is usually just to regulate the flow using the bath tap as its flow capacity is usually much higher and allows you to whizz water through the boiler before it gets the chance to say "hello" to it. Its counter intuitive to those who do not understand the workings of a combi (not you, but they are out there) and to persuade them that to get hotter water you turn the tap down. Some people look at you very strangely before you demonstrate it.

There is also the seasonal effect. At this time of year the water in the main is much colder and the boiler is rated usually to raise the temp by 35C at 12 l/min. So to get good hot water in winter you may only get decent hot water at...lets say 10 l/min as your starting point is much lower. Boiler makers are not beyond being sneaky and quoting 30c on the data sheet instead of 35c in order to claim it can do 14 l/min which is what the sales blurb will say.

Depending on the age of boiler, water hardness or cleanliness of the water in the heating system, there is also the possibility that the hot water plate heat exchanger is partially blocked by scale, sludge or a combination of the two. That can have a very debilitating effect on hot water performance. Also (and this may seem obvious...but) if there is separate control of the hot water temperature with a rheostat or other means of adjustment...then make sure its bang on maximum setting.
 
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Alfie168 said:
Be kind to Trolls.....
The answer with baths is usually just to regulate the flow using the bath tap as its flow capacity is usually much higher and allows you to whizz water through the boiler before it gets the chance to say "hello" to it. Its counter intuitive to those who do not understand the workings of a combi (not you, but they are out there) and to persuade them that to get hotter water you turn the tap down. Some people look at you very strangely before you demonstrate it.

There is also the seasonal effect. At this time of year the water in the main is much colder and the boiler is rated usually to raise the temp by 35C at 12 l/min. So to get good hot water in winter you may only get decent hot water at...lets say 10 l/min as your starting point is much lower. Boiler makers are not beyond being sneaky and quoting 30c on the data sheet instead of 35c in order to claim it can do 14 l/min which is what the sales blurb will say.

Depending on the age of boiler, water hardness or cleanliness of the water in the heating system, there is also the possibility that the hot water plate heat exchanger is partially blocked by scale, sludge or a combination of the two. That can have a very debilitating effect on hot water performance. Also (and this may seem obvious...but) if there is separate control of the hot water temperature with a rheostat or other means of adjustment...then make sure its bang on maximum setting.
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Alfie, many thanks for that. I try to be kind to everyone!
To start at the bottom of your post, age of the boiler is not a problem. I fitted it two weeks ago.
It happily copes with heating the water when the flow is restricted at the tap, I just want it to be easier for the "less technical" users to use. The boiler is a Valliant eco 350 (from memory) it works great, I'm just tinkering, which is why I plan to fit pressure and flow restriction to find which give the most consistent result.
Allan
 
Allan said:
Alfie, many thanks for that. I try to be kind to everyone!
To start at the bottom of your post, age of the boiler is not a problem. I fitted it two weeks ago.
It happily copes with heating the water when the flow is restricted at the tap, I just want it to be easier for the "less technical" users to use. The boiler is a Valliant eco 350 (from memory) it works great, I'm just tinkering, which is why I plan to fit pressure and flow restriction to find which give the most consistent result.
Allan
[/QUOTE

I'm sorry, I hadn't realised you were a gas fitter.
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Bilgediver said:
Actually Richard it is usual where only flow adjustment is required then the correct sized orifice inserted in the appropriate place is all that is needed. A PRV is total overkill.
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Except that the flow rate through an orifice will depend directly on the pressure available.
If you want the flow to be controlled, regulating the pressure is a good start.
A regulating valve is about £20 from Toolstation.
£20 does not buy you much of a plumbers time to experiment finding the right orifice.
10p for your orifice washer, £50 for knowing/deciding what sized hole perhaps?

I think it's quite common for mains pressure to vary a lot in some places.
In my house, a PRV is the only way as the mains can be above the spec limit for most boilers AIUI.

But a 35kW boiler should flow a lot of water to bath temp, unless the feed is meltwater from a glacier?
4.2kJ per degC per kg is the heat capacity
Say 5 degC in, 45degC out, 168kJ per litre, so 168kW would be 1 litre/s, 35kW should be 12.5 litres/min.
Maybe it's right.....
How much heat are you losing between boiler and bath tap?
 
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