Tundish dripping water

[Post and beam]

A tundish in our Cylinder cupboard is dripping enough water to splash out onto the floor. It is downstream of the Red pressure vessel.

I have not moved in yet and filled the water system to check for leaks on my second fix radiator installations. No heating is on.

[Nickfromwales]

Odd. 
 

Well, the waters coming from somewhere, so the question is; if the heating system’s not been filed why is the heating expansion vessel letting water out?!  
 

The gauge appears to be on zero, and I can’t see another feed teed into the pipe? Is that correct? 

[Temp]

12 minutes ago, Post and beam said:

I have not moved in yet and filled the water system to check for leaks on my second fix radiator installations. 

 

Did you mean you have or haven't filled it with water?

 

Pressure Relief Valves can be temperamental. Possibly just got a faulty one. If they are ever required to open (eg due to over pressure) they are prone to leaking even after the cause of the over pressure is removed. 

[Post and beam]

Water system was filled but no heat switched on. Pressure reading on the red vessel was just over 3 bar.

Now drained down again until i can get a professional to sort out my poor copper technique.

[Nickfromwales]

4 minutes ago, Post and beam said:

Water system was filled but no heat switched on. Pressure reading on the red vessel was just over 3 bar.

Now drained down again until i can get a professional to sort out my poor copper technique.

Ah. It’s supposed to be 1.5bar max as that’s the heating circuit. 
 

At >3bar the valve is doing what it’s supposed to have done, eg open to relieve the excess pressure, so no problem there.

 

Just refill to 1.5bar and check again. 

[Nickfromwales]

What’s wrong with the ‘copper technique’, all looks good to me!   

[Post and beam]

2 hours ago, Nickfromwales said:

Just refill to 1.5bar and check again. 

Hi Nick,

Do i open the isolator valve and just shut it off at 1.5 bar and let the rest of the system fill with water to whatever pressure it ends up at ?

If i shut its isolator what purpose is it serving .

[Nickfromwales]

1 minute ago, Post and beam said:

Hi Nick,

Do i open the isolator valve and just shut it off at 1.5 bar and let the rest of the system fill with water to whatever pressure it ends up at ?

If i shut its isolator what purpose is it serving .

 

If this is the ‘isolator’ then we’re referring to the “filling loop”. 
 

The black tap is a 1/4 turn which introduces cold mains water into your sealed heating system. 
 

You open that part way, and watch the gauge rise to 1.5bar, and then shut FIRMLY off.

 

Then you’d usually go around venting any air out, this would see the pressure drop to reflect the air (pressure) being let out. 
 

Then you’d top back up to 1.5 bar and then check the tundish 24hrs later. 

[Post and beam]

Thanks for confirming Nick, understood.

 

The poor technique i refer to is not what you see in the cylinder cupboard pictures here, i meant my poor compression fittings to the radiators and elsewhere. some of which leak slightly.

 

Mind you, reflecting on what you explained just now, if i filled the radiators to just over 3 bar i am less surprised that they show signs of leaks.

[Nickfromwales]

1 hour ago, Post and beam said:

Thanks for confirming Nick, understood.

 

The poor technique i refer to is not what you see in the cylinder cupboard pictures here, i meant my poor compression fittings to the radiators and elsewhere. some of which leak slightly.

 

Mind you, reflecting on what you explained just now, if i filled the radiators to just over 3 bar i am less surprised that they show signs of leaks.

I would like to give words of encouragement here, but you test at min 4bar and at 3 or a bit over, you defo shouldn’t have leaks.

 

Have you been using PTFE (min 13 turns on rad valves, I do 16) and pipe jointing compound on brass / nuts / threads / olives?

[Post and beam]

PTFE on Rad valves but 3 or 4 turns only. Need to revisit those.

 

Not used joining compound. I will now though.

 

I have read various conflicting things over the years about not needing to supplement olives for example. 

[Nickfromwales]

1 minute ago, Post and beam said:

PTFE on Rad valves but 3 or 4 turns only. Need to revisit those.

 

Not used joining compound. I will now though.

 

I have read various conflicting things over the years about not needing to supplement olives for example. 

3-4 turns is not enough. They should be a quick fix.

 

Pipe jointing compound is essential, so where a nut is tightened over a thread, and an olive is involved, you should fill the valleys of the threads (lightly) to reduce friction, which increases torque. 
 

Brass can bind early if done dry, hence the joint hasn’t then pulled quite as tight as it needs to. 

[Post and beam]

Got it

[Post and beam]

Now a new conundrum, I need to re do a compression joint that feeds a WC.  The upstream side is connected to a piece of copper that is in turn connected to a plastic pipe such that the copper spins freely when i try to undo the nut.

 

I hold the isolator valve with my grips and then undo the nut with a spanner, or rather, i dont becuase the copper pipe turns with it.. Is there a safe way to also grip the copper without risking crushing it?

 

I need 3 hands

 

 

[Nickfromwales]

15 hours ago, Post and beam said:

Now a new conundrum, I need to re do a compression joint that feeds a WC.  The upstream side is connected to a piece of copper that is in turn connected to a plastic pipe such that the copper spins freely when i try to undo the nut.

 

I hold the isolator valve with my grips and then undo the nut with a spanner, or rather, i dont becuase the copper pipe turns with it.. Is there a safe way to also grip the copper without risking crushing it?

 

I need 3 hands

 

 

Post a pic please. 

[SimonD]

On 06/10/2025 at 14:23, Nickfromwales said:

Have you been using PTFE (min 13 turns on rad valves, I do 16)

 

On 06/10/2025 at 14:48, Post and beam said:

PTFE on Rad valves but 3 or 4 turns only. Need to revisit those.

 

Loctite 55 is your friend here. Much better for people like me who are too impatient or lack the concentration to count all the way up to 16, and always get the PTFE spool round the wrong way. I used it for all me rad installs nowadays.

 

https://www.henkel-adhesives.com/uk/en/product/thread-sealants/loctite_550.html

[JohnMo]

1 hour ago, SimonD said:

Loctite 55 is your friend here

I started using it a couple of years ago after a recommendation on here. Works first time every time. Says on the packet how many turns are needed for different thread sizes so super easy and no guess work.

 

One my best purchases - makes life easy.

[Post and beam]

On 07/10/2025 at 10:29, Nickfromwales said:

Post a pic please. 

Apologies for not responding. Resolved. I was being a twat.

 

Grip the isolator tight enough and undo the nut. The spinning copper into the plastic fitting is irrelevant.