Overflow pipe running constantly

CarPark2

We have an overflow pipe coming from the hot water tank in the hotpress and running to the outside of the house. There is water constantly pouring out the pipe at the moment. The water is warm.

I have tried to trace the overflow pipe backwards and i am pretty sure it is coming from this pipe that comes from the hot water tank:




If i follow that pipe from the hot water tank, it leads to this junction:


As you can see, the junction is open and i can see a constant drip of water flowing from the horizontal pipe that emerges from the tank into the downward pipe. When i follow the downward pipe, as far as i can tell, that is the pipe that emerges from the gable end as an overflow pipe.

It is now 6 hours since we have had the heating on, and the water is still coming out of the overflow pipe.
Does this mean that the ballcock in the tank is broken? I presume this will require a plumber?

JustAThought

Not a plumber bit from many years of overflow shennanigans the ballcock is invariably the culprit and can be a relatively drama free thing to have fixed. I now have very hard water and now neighbours overflow pipes are routinely starting to flow night & day - one neighbours went for two years before they got into the attic and finally fixed it. Worth a look.

John.G

CarPark2 wrote: »

We have an overflow pipe coming from the hot water tank in the hotpress and running to the outside of the house. There is water constantly pouring out the pipe at the moment. The water is warm.

I have tried to trace the overflow pipe backwards and i am pretty sure it is coming from this pipe that comes from the hot water tank:




If i follow that pipe from the hot water tank, it leads to this junction:


As you can see, the junction is open and i can see a constant drip of water flowing from the horizontal pipe that emerges from the tank into the downward pipe. When i follow the downward pipe, as far as i can tell, that is the pipe that emerges from the gable end as an overflow pipe.

It is now 6 hours since we have had the heating on, and the water is still coming out of the overflow pipe.
Does this mean that the ballcock in the tank is broken? I presume this will require a plumber?

There is no ballcock in that cylinder, you have a unvented (pressurised) HW cylinder which is fed either directly from the mains (against regs) or from a pump via a cold water storage tank. Because hot water expands when it gets hot there should be expansion vessel close to the HW cylinder and this may have failed, it could also mean that the T&P valve is simply passing, just open a hot tap and see does the T&P valve stop flowing, can then advise further.

CarPark2

I looked up more on this.
The T&P valve is temperature and pressure. So it is to release water if the temp or pressure gets too high.
The thermostat for the tank is set to 60 degrees.

Any ideas on what is the most likely problem here?
Could the valve be malfunctioning?

John.G

Snap!, posted together.

listermint

CarPark2 wrote: »

I looked up more on this.
The T&P valve is temperature and pressure. So it is to release water if the temp or pressure gets too high.
The thermostat for the tank is set to 60 degrees.

Any ideas on what is the most likely problem here?
Could the valve be malfunctioning?

Get a plumber asap. Don't play around with heating and pressure related issues on your tank.

If not for the overflow relief there you'd have an explosive problem.

John.G

If installed "properly" there should be another PRV (pressure relief valve) installed after a non return valve on the cold feed, (the expansion vessel is often installed here as well as it last longer due to the cold water) this is called a expansion valve and is set 1 bar lower than the T&P valve so will lift before the T&P valve, another layer of safety as a expansion vessel must never be used as a safety device, I used to often see installations abroad with no expansion vessel but the expansion valve would pass a little each time the cylinder heated up.

CarPark2

Thanks.
I turned on the hot tap in the bath and ran it for 5 minutes. No noticeable change in the amount of water flowing from the TP valve.
I’ll take some photos now of the system and post them.

John.G wrote: »

There is no ballcock in that cylinder, you have a unvented (pressurised) HW cylinder which is fed either directly from the mains (against regs) or from a pump via a cold water storage tank. Because hot water expands when it gets hot there should be expansion vessel close to the HW cylinder and this may have failed, it could also mean that the T&P valve is simply passing, just open a hot tap and see does the T&P valve stop flowing, can then advise further.

CarPark2

Thanks for all the help with this.

Below is a picture of the overall setup. I can do close up photos of any parts of it if that helps.

There are two small tanks (red and blue) in the picture. Are they expansion tanks? There is a valve on the top of each one (like on a bicycle tyre). I pressed each one for a second. The red one has air in it, but the blue one doesn't seem to have any air. Is that significant?

There are two thermostats on the tank. The lower one is labelled control thermostat and it has a dial that can be set to different temperatures. it is currently set to 60 degrees. The upper one is labelled "high limit thermostat". That has a knob, but there are no temperature markers on it.

If installed "properly" there should be another PRV (pressure relief valve) installed after a non return valve on the cold feed, (the expansion vessel is often installed here as well as it last longer due to the cold water) this is called a expansion valve and is set 1 bar lower than the T&P valve so will lift before the T&P valve, another layer of safety as a expansion vessel must never be used as a safety device, I used to often see installations abroad with no expansion vessel but the expansion valve would pass a little each time the cylinder heated up.

Sorry, i am a complete novice here (i guess you may have noticed!). Do you see this in the picture? Where would i find the non-return valve on the cold feed?

CarPark2

This is the label on the tank, in case that gives more information:

CarPark2

Also, this is the pressure gauge. Seems OK?

John.G

That pressure gauge may be associated with the heating system, you may have no expansion valve fitted, the control stat is exactly that and would normally be set to 60/65C, the hi limit stat is a non settable hi temperature safety stat.
Can't really give more info on here, advise getting on to your plumber who may or may not be suitably qualified to fix the problems.

EVGR

JustAThought wrote: »

neighbours overflow pipes are routinely starting to flow night & day - one neighbours went for two years before they got into the attic and finally fixed it. Worth a look.

They probably wouldnt had wasted all that water if they had to pay for it.

Kencollins

Tap on the blue pressure vessel with something. Does it make a hollow ding noise, or a low dong noise?! If its low then it's probably full of water. The heated water expands, has nowhere to go, and ends up releasing the 6 bar valve.

CarPark2

Kencollins wrote: »

Tap on the blue pressure vessel with something. Does it make a hollow ding noise, or a low dong noise?! If its low then it's probably full of water. The heated water expands, has nowhere to go, and ends up releasing the 6 bar valve.

Thanks. That was at least part of the problem. A plumber came out to look at it and the blue tank was full of water, so he pumped it with air.
But also the T-P valve needed to be replaced.

Kencollins

CarPark2 wrote: »

Thanks. That was at least part of the problem. A plumber came out to look at it and the blue tank was full of water, so he pumped it with air.
But also the T-P valve needed to be replaced.

Glad you got it sorted!

Those T+P valves are often "one shot". Once they are opened they don't seal properly again a lot of the time due to scale build up.

I'd be fairly sure the blue pressure vessel was the cause of the high pressure. Keep a check on it, as the membrane may be letting the air through slowly.

John.G

Or it could be the schrader air filling valve leaking.

CarPark2

Previously the water was flowing constantly from the T-P valve. Since it has been replaced, no water flows most of the time, but if we turn on the oil boiler and turn down the room thermostats (i.e., so that the oil boiler is just heating the hot water tank and not the radiators), water comes from the T-P valve.

So it seems that the the oil boiler keeps heating the water in the tank, to the point that the T-P valve is activated. Should there not be a feedback loop that turns off the oil boiler when the water in the tank gets hot enough?

To explain:
Our heating system is semi-zoned!
There is a thermostat upstairs and another downstairs.
We were advised that it is cheaper and more efficient to heat the hot water tank from the oil burner than from the immersion.
So, if we want hot water, we put on the oil boiler and turn down the room thermostats upstairs and downstairs. This stops water flowing to the radiators gets the water in the taps nice and hot. If the room thermostats are set to room temperature, the hot water from the taps gets warm, but not really hot enough for washing dishes or for a bath.

Kencollins

CarPark2 wrote: »

Previously the water was flowing constantly from the T-P valve. Since it has been replaced, no water flows most of the time, but if we turn on the oil boiler and turn down the room thermostats (i.e., so that the oil boiler is just heating the hot water tank and not the radiators), water comes from the T-P valve.

So it seems that the the oil boiler keeps heating the water in the tank, to the point that the T-P valve is activated. Should there not be a feedback loop that turns off the oil boiler when the water in the tank gets hot enough?

To explain:
Our heating system is semi-zoned!
There is a thermostat upstairs and another downstairs.
We were advised that it is cheaper and more efficient to heat the hot water tank from the oil burner than from the immersion.
So, if we want hot water, we put on the oil boiler and turn down the room thermostats upstairs and downstairs. This stops water flowing to the radiators gets the water in the taps nice and hot. If the room thermostats are set to room temperature, the hot water from the taps gets warm, but not really hot enough for washing dishes or for a bath.

Interesting issue!

Could the heating coil in the hot water tank have failed, allowing the central heating water to pressurize the hot water tank? If the heating expansion tank is being closed off due to zoning, it could be going quite high causing the issue seen. Not a very likely scenario though.

astrofool

CarPark2 wrote: »

Previously the water was flowing constantly from the T-P valve. Since it has been replaced, no water flows most of the time, but if we turn on the oil boiler and turn down the room thermostats (i.e., so that the oil boiler is just heating the hot water tank and not the radiators), water comes from the T-P valve.

So it seems that the the oil boiler keeps heating the water in the tank, to the point that the T-P valve is activated. Should there not be a feedback loop that turns off the oil boiler when the water in the tank gets hot enough?

To explain:
Our heating system is semi-zoned!
There is a thermostat upstairs and another downstairs.
We were advised that it is cheaper and more efficient to heat the hot water tank from the oil burner than from the immersion.
So, if we want hot water, we put on the oil boiler and turn down the room thermostats upstairs and downstairs. This stops water flowing to the radiators gets the water in the taps nice and hot. If the room thermostats are set to room temperature, the hot water from the taps gets warm, but not really hot enough for washing dishes or for a bath.

There should be a thermostat on the hot water tank that will tell the boiler when to turn off, otherwise it will keep running hot water (and exceed the required temperature causing the overflow to happen) until you manually turn it off.

It is more efficient to heat the hot water with oil than electricity, but only if you turn off the oil when it gets to the required temperature.

Wearb

astrofool wrote: »

There should be a thermostat on the hot water tank that will tell the boiler when to turn off, otherwise it will keep running hot water (and exceed the required temperature causing the overflow to happen) until you manually turn it off.

It is more efficient to heat the hot water with oil than electricity, but only if you turn off the oil when it gets to the required temperature.

The boiler control thermostat will prevent the water getting to a temperature that would cause an Overflow, even in the absence of a thermostat on the hot water tank.

CarPark2

Thanks for all the replies. Sounds like i need to get the plumber back to have another look.

John.G

Presume your service person knows that the blue vessel should be pre filled (with air) with it empty to at or just below the cold water mains or pumped cold water supply, ie, if the cold pressure is 2 bar, the air pre pressure should be 1.8/2.0 bar.

CarPark2

John.G wrote: »

Presume your service person knows that the blue vessel should be pre filled (with air) with it empty to at or just below the cold water mains or pumped cold water supply, ie, if the cold pressure is 2 bar, the air pre pressure should be 1.8/2.0 bar.

I don't know what he knows to be honest! When he came last week, there was no air in the blue vessel. I think he just pumped it and brought it up to 2 bar.
Given that it is in position and connected, i don't know how it could be "pre-filled".