Water from a vent pipe

[doitall]

Mains water is reaching the DHW cylinder (at the top, i.e. the hot outlet), displacing the hot water within, and forcing it back up the cold feed (from the base of the cylinder) into the CSS.

For anyone who's still wondering why it does that, it's all down to pressure - the head of water in the vent is the same as that of in the cistern, so the water level will rise in both. It won't come out of the vent simply because it overflows from the cistern first.

My original comment was meant as a joke just in case you wondered.

However you still don't get it, The head of water in the vent is the same as that of the cystern (tank) That is until you backfeed it with MAINS pressure the water will go straight passed the cylinder (see drawing) and out the vent [/b]

 

[Softus]

The test for the theory, as doitall correctly pointed out, is to shut off the cold mains...

You specified the correct test but you gave the wrong explanation of the flow of water - one day you'll understand that you got that part of it wrong, which is all I've ever said that you got wrong.

Yes it is see drawing

It doesn't help anyone's understanding to quote a big wodge of text and insert a tiny and snide comment.

In point of fact, the drawing illustrates perfectly how wrong you are about hot water coming from the vent pipe - well done.

 

[doitall]

Mains water is reaching the DHW cylinder (at the top, i.e. the hot outlet), displacing the hot water within, and forcing it back up the cold feed (from the base of the cylinder) into the CSS.

How can the cylinder pressurise to be able to force the water up the cold feed. It cannot, Its Impossible.

 

[Softus]

My original comment was meant as a joke just in case you wondered.

I wasn't wondering, but I am now. If I missed the joke then of course I'll reconsider, but could you point me towards it 'cos I still can't see it!

However you still don't get it, The head of water in the vent is the same as that of the cystern (tank) That is until you backfeed it with MAINS pressure the water will go straight passed the cylinder (see drawing) and out the vent

Oh I get it alright. I get this:

1. Your theory about water coming the vent.
2. The theory is wrong.

The reason you're wrong is because you believe the head of water changes when you apply back pressure. The head of water is the pressure of water that results from it being at that height, and it only increases when you increase the height of the water. Applying mains pressure to it will overcome the pressure (in most domestic installations), and it will do so be pushing water up BOTH the cold feed and the vent. However, it will only flow from the cold feed, because the vent pipe rises above the water level in the cistern.

How can the cylinder pressurise to be able to force the water up the cold feed. It cannot, Its Impossible.

Fine - go ahead and believe that it's impossible. Why don't you go and test your theory and check that you're correct?

I'm going to stop telling you now, because I'm starting to feel embarrassed on your behalf. One day it will click, and you'll understand.

In the meantime I'll leave JohnD and others to try and get through to you. My work is done here.

 

[doitall]

In point of fact, the drawing illustrates perfectly how wrong you are about hot water coming from the vent pipe - well done.

Connect the red and blue line together, and simulate the fault, turn the mains on, where is the water going, UP THE VENT and OVER THE TANK.

You are forgetting the mains pressure will be greater than the tank.

 

[doitall]

The reason you're wrong is because you believe the head of water changes when you apply back pressure. The head of water is the pressure of water that results from it being at that height, and it only increases when you increase the height of the water. Applying mains pressure to it will overcome the pressure (in most domestic installations), and it will do so be pushing water up BOTH the cold feed and the vent. However, it will only flow from the cold feed, because the vent pipe rises above the water level in the cistern.

How can the cylinder pressurise to be able to force the water up the cold feed. It cannot, Its Impossible.

Fine - go ahead and believe that it's impossible. Why don't you go and test your theory and check that you're correct?

I'm going to stop telling you now, because I'm starting to feel embarrassed on your behalf. One day it will click, and you'll understand.

In the meantime I'll leave JohnD and others to try and get through to you. My work is done here.

The mains pressure could be several bar higher than the tank pressure, How can the mains water get into the cylinder, it has an open vent.

Don't feel embarrassed on my behalf, because you know your wrong.

 

[Softus]

I've love to hear your theory about why the CSS has warm water in it then!

Why don't you go and test your theory and check that you're correct?

I'll leave JohnD and others to try and get through to you. My work is done here.

 

[doitall]

I've love to hear your theory about why the CSS has warm water in it then!

Why don't you go and test your theory and check that you're correct?

I'll leave JohnD and others to try and get through to you. My work is done here.

How can the mains water pressure get into the Cylinder via the hot pipe See Drawing it cannot for the last time.

The OP said the water is coming out the vent.

 

[Softus]

//www.diynot.com/forums/viewtopic.php?p=387658#387658

 

[doitall]

I've love to hear your theory about why the CSS has warm water in it then!

Why don't you go and test your theory and check that you're correct?

I'll leave JohnD and others to try and get through to you. My work is done here.

How can the mains water pressure get into the Cylinder via the hot pipe See Drawing it cannot for the last time.

The OP said the water is coming out the vent.

Same answer.

 

[Registered Gas Man]

Can i add to my post count as well plz!

 

[doitall]

I have modified the drawing to show the fault condition, where the mains water is creeping back into the hot pipe via the faulty/sub standard valve.

Depending on the amount of backflow this will blend with the hot and dump warm water into the tank via the vent, it , Cannot enter the cylinder, unless the vent is blocked

 

[doitall]

Can i add to my post count as well plz!

Of course you can especially if you have an opinion

 

[Nige F]

If the gatevalve in the drawing is shut D-I-A is right .........if it`s open Soft. is right Now then , back to the jet plane and the conveyor

 

[JohnD]

hahahahaha!