Overflow from vented C/H exp tank dripping - but ball cock not at fault?

[barki]

Hi

I've got a open/vented system in my 1990's two story house.

There are two tanks in the attic, one large cold water tank, and one smaller c/h expansion tank. Both tanks are fed by 15mm cold mains via a ball valve.

The overflow pipe from the smaller tank drips (slowly, but regularly - enough to soak the doormat beneath it).

Anyway, I assumed that the ballcock/valve from was getting old and needed replacing. I just went up to have a look and was disappointed to find that whilst the valve is old and rusty, its not dripping, or 'spraying'. It seems to operated on/off just fine.

What I did notice though, I that the water in the C/H tank was hot - and I havn't yet turned on the C/H this year (saving pennies as long as we can!). I can only conclude that hot water is coming on via the hot water cylinder overflow (cylinder in airing cupboard on the 1st floor). However the water in the tank was a good two inches below the height of the overflow pipe that it is dripping from. Im a bit perplexed by that.

None the less, if the hot water cyl is overheating, and overflowing into the C/H Expansion tank, and then dripping from the overflow into the garden, what's my next step to identify the cause?

Do I look at the thermostat on the Cylinder?

Cheers in advance if anyone can help

Tom

 

[picasso]

Its probable that the coil in the cylinder has a pinhole and thats causing the overflow in the c/heating tank to drip, time for a new cylinder if thats the fault.

 

[barki]

Cheers for the response - I was worried someone would give a response like that tho, argh!

I put an S-flange on the cylinder for the shower pump, and replaced the 3-way valve a while back, but I think full cylinder replacement is beyond my DIY ability


How can I be sure? I cant see if the cyl expansion pipe that runs into the C/H tank is actually dripping, because the end of the pipe is under the water level. Can I cut it a few inches sort to watch for drips?


Also - it doesn't explain why my C/H tank is hot? Surely it must be more than a drip getting in there....?

One more thing - I notice that the ball valve for the larger cold tank DOES drip...perhaps i'll replace that anyway just as a matter of course...



Cheers,

Tom

 

[barki]

P.S - Will raising the height of the C/H tank to the same height as the top of the water level in the cold water tank prevent water running between the two via the pin-hole in the coil (if there is one?)

 

[picasso]

Stop the feed to both loft tanks, empty the feed and expansion then wait and see if the feed and expansion refills, turn off the heating and hot water and dont use any water for a couple of hours.

 

[picasso]

P.S - Will raising the height of the C/H tank to the same height as the top of the water level in the cold water tank prevent water running between the two via the pin-hole in the coil (if there is one?)

Yea if you dont mind your bath water being contaminated with the gunge in your radiators.

 

[DaveHerns]

If your expansion pipe is below water level are you not getting a syphon/circulating effect ? The expansion pipe should rise up high , loop back and end up above the level of water in the tank,

 

[leakydave]

I was just going to say the VENT pipe MUST be above water level, but also that the cylinder coil is probably passing water.

 

[Agile]

You said something illogical. That water was 50 mm BELOW the over flow connection but it was still dripping!

Are you sure the CW tank is not overflowing and the two overflow pipes are joined?

Lets assume the over flow is from the F&E tank and when you are not looking it rises up to the overflow. That will imply a faulty cylinder coil.

The level in the F&E tank should only be 100 mm.

Empty excess water and check the ball valve is only filling to that level. If not then bend the arm to set it correctly!

At the correct level the vent pipe should be about 150 mm above the water.

When CH is on the expansion of the system water will cause the level to rise about 50-100 mm depending on the water content of the system.

So when its all correct note if its pumping over from the vent pipe and monitor the water level.

Tony Glazier

 

[barki]

Hi

Thanks very much to you all for the responses -Just got home. The overflow dripping still (slowly, as always). Checked the CH tank, level of water NOT up to the pipe. Level of water about 110mm deep (I assume this is tolerable, its well over the inlet, and well under the overflow). But the VENT pipe (as someone above corrected me) is a cm under the water level. Water is hot. Lots of condensation on inside of box lid.

Im beginning to think that steam, caused by the siphoning/circulation of the vent pipe being submerged its what's dripping out of the overflow and I supposed it condenses in the pipe and then takes the slow-downhill route towhere the pipe leaves under the eaves.

I've just cut that vent pipe back, now so its approx. 12-15cm above the water level.

Will report back in few hours!!



(P.S. Someone asked earlier if the overflow was connected/t juctioned etc anywhere - no its not, I can trace it from the points where it drips, all the way to the overflow hole in the CH tank, and yes, the water level is below this,, even when its dripping.)

 

[barki]

Hi

I just thought if anyone reads this in the future they might want to know the solution - The problem has been solved just by cutting back the vent pipe slightly at mentioned above.

There is now no dripping, no condensation, and the water in the tank isn't hot. Tested for two days, seems fine. Tide mark inside the tank confirms that water level never reached the overflow, but condensate from the hot water was building up in it, and dripping out at the other end.


Thanks very much to all who replied

Tom

 

[Agile]

It was totally illogical when you said water level was BELOW the over flow but it was still dripping.

But as you suggest it must have been caused by condensation from the hot water vapour caused by the pumping over.

The reason I did not think of that is because you had not mentioned there was a lid on the tank. Very few of those I see ever have the lid on although of course there should be.

Congratulations on solving a simple problem!

Tony

 

[PullerGas]

Sure it's not pumping over?? Where's the CH expansion pipe connected?

 

[Nige F]

Sure it's not pumping over?? Where's the CH expansion pipe connected?

And is the cold feed blocked ? I had the exact same thing here and it was the cold feed blockage - replaced connections with an airjec from eBay