Dumb Question I think.

[Winston]

If my current Cold Water Storage Tank feed to the Hot Water Cylinder is in 22mm if I was to change this to 28mm would this improve the hot water pressure or volume? Or would it make no difference if the HWC supply remains at the 22mm?

My reasoning behind this question is that the additional cold water supply to the hot water cylinder would increase and thus force the hot supply out of the cylinder at a increased rate.

 

[helpsy]

Wouldn't you have to upgrade the hot outlet to 28mm to get the same flow out as in?

 

[dontknowitall]

Not a dumb question and I'd like to know the answer as well!!

To be honest I'm not sure it would make any significant difference whereas positioning the CWSC higher up (if possible) or installing a larger tank (if possible) might make some difference. I think increasing the width of the pipe would increase the flow rate but not the pressure, but both are related of course.

Is the CWSC vertically above the hot water cylinder? This is exaggerating but I suspect if the cold storage is at one end of a house with the hot water cylinder at the other end this would create pressure problems.

I'd still like to know the correct answer.

 

[Bernie2]

In self contained flats they nearly always increase the cold feed to 28mm. They don't have the head height to higher the storage cistern to gain extra pressure.

By making the supply pipe bigger, they increase the flow not the pressure.

But then if its the amount of water you want, its a good idea. But if you want to force the water around something it makes no difference.

In short if you want to fill a bath using ordinary taps, its great, but for high resistance shower or mono bloc mixer its questionable, but still a help.

 

[Winston]

Many thanks guys I did wonder that was all a moment of my madness I might give it a go on my house and let you know if any difference.

 

[justlead1]

Hi. A larger cold feed is used when the draw from the cylinder is greater than the cold feed delivery. (CWSC only just above cylinder and hot supply serving say the floor below) the suction on the hot supply pulls air down the vent as the cold feed can not feed cylinder quike enough. This situation manifests itself with squirts of air from tap (usually bath) at few second intervals. Good Luck

 

[dontknowitall]

Thank you Justlead. That one's definitely worth tucking up my sleeve for future reference.

 

[Bernie2]

Thanks Justlead!

I had completely forgotten about that problem.

That's Plumbing though, so many things to get your head around its easy to forget, just as well we can come on here and get reminded.

 

[stevetheplumber]

imho it will not increase anything unless the outlet is upsized as well a said it will stop suction on the vent in low head situations only raising the tank will increase preasure but up sizing both in and out would help flow rates

 

[radswilldo]

Steve is correct, if there was any increase it would be minute. The pressure is the same, pipework from cylinder the same

 

[Winston]

Ok I was right in a way It was a dumb question

 

[radswilldo]

No it wasn't as you now have an answer

 

[pauls]

i dont think there is ever a dumb question someone out there will also want to know the same thing but wont ask the question

 

[dontknowitall]

When I was on my plumbing course, during one of the first lessons we were talking about turning the mains off and cutting through the cold water supply.

I suggested (dumbly?) that all the water from the house would fall back to that point (under kitchen sink or wherever) and surely there would be a lot of water swilling around the kitchen.

Just about everyone came up to me afterwards and said, "I'm glad you asked that question cos I was too frightened to ask it myself"!!

No such thing as a dumb question as far as I'm concerned. Dumb answers, yes (I'm guilty of that one) but no one can be expected to know everything.

 

[Puddle]

So thats it settled then,we have decreased the pressure on Winston to increase the size of his supply pipework to his cylinder ,as this would infact not increase any pressure through outlets,,however we have now increased the pressure from his partner to rise the tank to increase the said pressure to the cylinder,thus outlets,that Winston thought ,may be gained from increaseing the size of the supply pipe,I do like it when it all comes togeather

 

[stevetheplumber]

So thats it settled then,we have decreased the pressure on Winston to increase the size of his supply pipework to his cylinder ,as this would infact not increase any pressure through outlets,,however we have now increased the pressure from his partner to rise the tank to increase the said pressure to the cylinder,thus outlets,that Winston thought ,may be gained from increaseing the size of the supply pipe,I do like it when it all comes togeather

next stop carpentry forum winston how to build a stand lol

 

[Bernie2]

Hmm!

I found some most of this out the hard way.

Yes you can get soaked if your in a big house and you cut the water main downstairs. It kids you on mind, because if the rising main is full and the ball valve and any cold taps are off, the water holds in the vacuum. The minute they get opened you get wet.

Bigger pipes usually mean more flow. You may get the impression your getting more pressure but the increase is minute and is not really a pressure gain more a reduction in head loss/resistance.

The only places you get pressure from, is what ever the water main will give you, the height of your stored water tank, or a pump system.

In reality of course the main could be said to be stored water from the reservoir or local water tower and it depends how low you are on the hydraulic line how much pressure you get, or you may be near a pumping station if the mains pressure is pumped.

That is why if you have got lousy mains pressure an unvented cylinder or combi isn't much use to you, regardless of how much flow they say it will deliver, unless of course you fit an approved booster system on the mains water supply.

And don't forget we are talking dynamic pressure not static.

The resistance of the system and fittings is also part of the reason people may choose to use pumped power showers or complain about poor showers.

Lets be honest, on some of the modern showers it appears you would need a water pressure the same as a jumbo jet's engine thrust to force the water through the hose and head.