hot water storage tank overflow

[aero]

I recently noticed that there is water coming out of the overflow on the side of my house. After a bit of inspection, I see that the hot water storage tank is overflowing into the hot water header tank (which now contains extremely hot water). I also see the the ball valve in the header tank is leaking, adding additional cold water to the header tank.

If i fix the ball valve, does that solve my problems? or is there a poblem with the storage tank as well? (i have just moved into the house and there was no problem with the overflow when i moved in, so i suspect that something has deteriorated - probably the ball valve?)

 

[Alanka]

You seem a little confused about what tanks do what!

You should have a large cold water tank which supplies the hot water cylinder and possibly other appliances with cold low-pressure water. You should also see a much smaller feed & expansion 'header tank' that takes up the expansion of the inhibited boiler water circulating in the radiators and heating the hw cylinder.

Each tank has its own overflow pipe to outside, usually at eaves level. You should first determine which of the two tanks is overflowing. If it's the large cw cistern you can service or replace its ball valve.

If it's the smaller F&E tank it could be the ball valve letting by, and/or it might be something else. If hot water is coming out of the F&E vent pipe (the 22mm pipe that bends over and into the tank from above) you may have a blockage in the 15mm pipe that exits the F&E tank near the bottom, and goes down to the boiler or air separator. [Less likely is that your circulating pump is working too hard and causing 'pumping over' - why should it suddenly start doing this?] If a blockage, try clearing it with a curtain rod or special 'snake', or sucking it out with a 'wine pump' or plunger applied to the drain hole in the tank. A blockage can occur suddenly if a lump of crap in the bottom of the tank decides to move down into the pipe.

Hope these ramblings help!

 

[Phil]

Worrying, do you have an electric immersion heater on the hot water cylinder?

If the thermostat on these fail then the water in the cylinder will boil and expand up the vent (hangs over CWS tank) and fill it with hot water causing it to overflow.

You need to check to see it the immersion switch is off, also sort the ballvalve out.

Also mains cold could be passing into gravity hot through a dodgy mixertap, shower washing maching etc.......

 

[Alanka]

Phil rightly says that a faulty immersion heater thermostat in your hw cylinder can pump hot water up and into your large cw storage tank - which can be, and has been, lethal if the plastic tank softens and collapses.

However, you say that it's the smaller 'header' (F&E) tank that's getting hot - which could be caused by the scenario I outlined in my previous post, and is not very dangerous!

 

[Phil]

mmmm......

Although aero's wording is wrong it does read like its the cylinder/CWS tank.

Come on aero, which tank is it big or small, do you have a smaller F+E central heating tank?

 

[aero]

Ok. Here is the status update. I can confirm that it is the smaller F&E tank

There are two water inlets into the small tank: (1) ball valve - cold water (2) a copper 22mm pipe which I now assume to be the "vent pipe" from which hot water is coming out, possibly directly from the boiler (i followed it as far as i could).

I have now replaced the ball valve that was leaking cold water into the tank and that part of the problem is solved.

i have also worked out that if i turn the central heating off then no more hot water pours into the tank. As soon as i turn the heating back on (after a few hours), water immediately comes out, initially cold then hot. This suggests to me that this is not a problem of water expansion due to heat.

I have reduced the float level and partially emptied the tank but the hot water keeps coming. Opening the hot / cold water taps does not reduce the flow of the hot water.

thanks for your enthusiasm to solve this problem! most appreciated.

i shall attempt to clean the exit pipe at the bottom of the tank.

out of interest, i can hear that the large tank float is also not sealing and it is also needs replacing. i have no idea if this influences the situation.

 

[Puddle]

well you could try turning the pump down
persume has been working ok so pipework should be ok

or you have a blockage/restriction in the heating system,try pooring a mild system cleaner in the header tank
How old is the system,what boiler is it
siduation needs correcting asap as pumping over allows fresh corrosive water into system,attacking rads and boiler

 

[quality]

Sounds to me that the coil in the indirect in split

 

[aero]

Progress report 2:

I have established that the water is simply recycling. Now that i have fixed the float valve, the level of water does not increase even though the hot water continues to flow into the H&E tank. This means it must be flowing back into the system as fast as it flows into the tank (flow rate is a steady trickle)

As a result, there is no more overflow but the H&E tank is very hot.

my assumption is that a small portion of water is being diverted to the H&E tank. Perhaps there is a blockage in the heating system?

Puddle recommends turning the pump down. Is the pump in the boiler or will it be somewhere in the system? i presume there is a screwcontrol or some such device to slow it down?

thanks all

 

[stevetheplumber]

Progress report 2:

I have established that the water is simply recycling. Now that i have fixed the float valve, the level of water does not increase even though the hot water continues to flow into the H&E tank. This means it must be flowing back into the system as fast as it flows into the tank (flow rate is a steady trickle)

As a result, there is no more overflow but the H&E tank is very hot.

my assumption is that a small portion of water is being diverted to the H&E tank. Perhaps there is a blockage in the heating system?

Puddle recommends turning the pump down. Is the pump in the boiler or will it be somewhere in the system? i presume there is a screwcontrol or some such device to slow it down?

thanks all

in your case its most likley to be part of the systen although it could be inside the boiler casing or in the airng cupboardwhen you find it there is a switch on the side usually with three settings set it to low see if this stops the filling of the tank if yes leave it there and see if the heating still works if heating is slow to work go up one and repeat what youve tried

 

[REDSAW]

do your rads actually get hot, very hot all over all of them?.
t.r.v''s on all of them bar one?.
the heating water is expanding and has no where to go but to the course of least resistance, in your case up.

 

[aero]

Problem has returned! Even with the pump on level 1 there is still flow into the H&E tank (which is very hot). I have opened all the radiators valves to max to reduce resistance but it makes no difference.

I have now clearly established the link to the pump. Turn it off, no flow, turn it on and flow recommences within a few seconds. This is quite frustrating I tell you!

I will introduce a cleaning agent today and see what happens.

thanks all

 

[Alanka]

Did this problem suddenly start, or is it that you've only just noticed it? Was the system working fine up till now? How long have you lived at this address with the current heating/hot water system?

It's sounds like 'pumping over' but why should it suddenly start after working OK?

Can you tell us if the vent pipe (22mm, going up and over into the F&E tank) is connected downstream of the pump or upstream (i.e. on the high pressure output side of the pump or on the low pressure inlet side)? It's on the inlet side usually, but not always. And on what side is the 15mm feed pipe (from the base of the F&E tank) connected? Should be same side as vent pipe, and within a few inches of it, but may not be.

 

[aero]

Hello Alanka,

I moved in 3 months ago and noticed the problem a week ago when the water started coming out the overflow on the side of the house. This was due to the faulty ball valve which i have now fixed.

it is pretty impossible for me to say how long the hot water has been flowing out the vent pipe for but i think it must be a while. i notice that the water in the H&E tank is very very rusty so there must have been some considerable circulation from the system but then i suspect the system has been around for a good couple years. Also, the previous owner has insulated the H&E tank suggesting he must have known... but then i see that he also insulated the cold one as well.

as for it being on the high / low pressure side, i think it is low pressure (the pipe disappears into the wall so cannot follow it) but there is a lag of a good few seconds after initiating the pump before the water comes out. Any particular way i could tell without follwing the pipes?

15mm outlet is on the same side and yes, the 22mm goes over the top of the H&E tank.

of interest, the small tank is on the same level as the large tank, but the large tank water level is above the water level of the small tank. i am not sure this is relevant as the small tank water level does not fluctuate now that i have fixed the ball valve.

doesnt make much sense.

on another note, the person who put this in made a right mess of the wiring and has manged to make the 3 prong plug that they use to power the pump live! i got a hell of a shock from the plug! pulled out the faithful voltmeter to discover that the neutral of the 3 prong plug is 230V whenever the bolier is on! i wasnt very happy about that. the fact that they even used a plug at all considering the power comes from the boiler tells me that these were no experts!

you wouldnt by any chance have a wiring diagram for the operation of the pump and valve would you? (i am very comfortable with electricity - except when it comes out the plug and not the socket!) i want to rewire the junction box and make sure the earth has been properly connected. (there are two incoming 5 core cables from the boiler which must operate the hot water and heating - i havent checked them out properly just yet)

thanks for your interest and ongoing help

 

[stevetheplumber]

Sounds like this has been like this for ever or could be caused by a blocked cold feed try draining a little with the balvalve of seee if tank empties or its a design fault which will beed repiping to boiler manufacturers spec
alternative is to seal the system up with addition of a preasure vessel filling loop and saftey valve but not all older boiler permit this
wiring diagrams are available from the honeywell website

 

[aero]

Hello Steve,

Thanks for the feedback. I agree that this is almost certainly a design fault. I will add some cleaning liquid and see if that helps.

Other than that, I agree with adding a pressure valve. What do you mean by a "pressure vessel filling loop"? Can I not just stick a valve inline?

Once again, thank you - Great forum with very helpful people

 

[hewie]

I'xe had a similar problem twice in a period of 20 years, it was a rupture in the hot water cylinder coil. replaced HW tank problem solved

 

[Phil]

Aero, don't forget when you add the de sludging agent into the F+E tank make sure you open a drain cock downstairs to draw it into the system or it will just sit in the tank doing nothing.

As said if your boiler permits you can ditch the F+E (feed and expansion) tank and replace with an expansion vessel and filling loop, the latter allows you to manually fill the system and the vessell takes the expanding water.

 

[REDSAW]

pumps on the right way round is it?.

 

[aero]

Thanks for the explanation Phil. Makes sense now.

Just looked up the expansion vessel on the screwfix website. How do i know what size to install?

As for the desludging agent, point taken, thanks. In my last house I ran a length of plumbing directly into the drain with a stopcock so that i could empty the system with ease. I suspect i am going to miss that little function.

redsaw:
are you asking for the make and model of the pump?

 

[oldie]

Not a plumber so just my 2p's worth
I had the same problem when we moved into this house expansion tank full of very hot water and loft full of steam, it turned out that some time in the 30 years before we purchased the house a cheap hot water conversion had been carried out by installing a direct conversion tube ( or what ever it was called) into the cylinder ( sort of a three flattend tubes joined at top and bottom) instead of replaceing the water cylinder to one with a integral heating coil. to cut a long story down , the flange on bottom of this tube had dropped off allowing the water direct from the boiler to "leak" into the cylinder as it had nowhere to go it went straight up the expansion pipe into the header tank. The cause, either age or corrosion I can't remember, but once the cylinder had been replaced problem solved.
oldie