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Discuss Header overflow - should be so simple. in the Plumbing Jobs | The Job-board area at PlumbersForums.net

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Header tank overflows.
Has 4 connections
2 x 18mm mm distribution both fitted with non return valve,
1 x 15mm [pressure limited 4 bar] supply via ball valve,
1 x 18mm overflow waste discharge to eaves.
Also theres 1 x 18mm pressure releif line from cylinder cupboard which terminates over the tank. This has a jam jar suspended below it to prove its not discharging back to the tank - it's dry.
The overflow discharges - usually overnight.
The ball valve assembly has been replaced with new - more than once and with differing types to no avail - there are no obvious leaks at this point!
Still there's an overnight discharge.
HOW?? What else can possibly be wrong?
 
Backing up through the cold feed check in the morning is the tank water inside the tank warm / hot
 
Backing up through the cold feed check in the morning is the tank water inside the tank warm / hot
Hi Shaun,
As they leave the tank the 22mm h and c distribution lines are fitted with non return valves. They serve down to a 2 bar dual pump which is off overnight to manage any noise issues.
Water heating is controlled to times outside the overnight period so no reason for expansion issues during the night.
System has been fine for 30 years. It is now recently causing problems but nothing has been changed for years save for the recent addition of non return valves and replacement ball valves and float assemblies.
Heating is a sealed pressurised system and holds steady at about 1.5 bar, so no cross link leak otherwise pressure would vary.
Aother point there's a ballofix in the 15mm supply close to the tank. If I isolate this the problem ceases. This factor points hard to the float valves but I have now fitted 5 with 4 differs and none have stopped the problem. No duffer could get all 5 installed to fail.
One last point when installed I am setting the float arm to close off at overflow minus about 70mm so it's gaining gallons not pints to reach the overflow.
Really, logic denies that this problem can continue but it does!!
 
Backing up through the cold feed check in the morning is the tank water inside the tank warm / hot
Hi Shaun,
Still in need of more help here!

Header tank temperatures remain ambient - not warmer than surroundings.

First fitted the non return valves on the distribution pipes just over a couple of days ago to be sure to prevent any back flow to the tank from them.

There's still an ongoing issue except when I isolate the 15mm supply.

Also, since installing the non return valves on the distribution lines and with the supply line ballofix open there's been about a half cup of water discharged [over 24 hours] to the container which I positioned under the distribution system overflow pipe [the one which vents and drains over the header tank and therefore one that could fill it].

To my mind this suggests that there's minimal back pressure in the distribution side. Probably nothing more than that generated when shutting a ceramic tap off reasonably quickly against the operating 2 bar pump. Anyone disagree with this assessment?

During this same time water levels in the header raised from minus 70mm to overflow - so again to my mind the water gain just has to be either via the non returns or via the float on the supply otherwise that small vessel [a small jam jar] would be full to overflowing and it isn't!

Seems I may need to remove the non return valves again long term [any comments anyone?] but first I needed to confirm that there's been no significant backflow to the header via the distribution lines.
Adding them seems to have made no obvious difference to the rate levels can build in the header tank so perhaps I just take them out again?

HELP please!
 
TBH you shouldn't need to install non return valves also best option is to get a plumber out to look at your system as its a unique
 
Is there a branch between the ballofix and the ball valve?
If so, where does it go to?
 
A distributing pipe feeds taps.
A cold feed feeds a cylinder.
Usine the definitions I have given, do you have 2 distributing pipes, or 1 distributing pipe and 1 cold feed, coming off that cistern?
 
Hi Ric2013
There are two 22mm outlets leading from the base of the cw storage header to the cylinder cupboard at 1st floor. One serves cw feed to the hw distribution and the other is the cw distribution.
In detail:
From the cw storage 1 cold feed drops to the base of the coil in the immersion cylinder, then the h distribution runs from the head of the coil and connects to the h inlet of a two bar pump with the h outlet then re connected to the old distribution pipe again.
The other cw distribution drops to the cw pump inlet and the cw outlet is reconnected to the distribution pipework.
TBH you shouldn't need to install non return valves also best option is to get a plumber out to look at your system as its a unique

[Question - the pump is a dual pump h and c - is there potential for a backfeed from h to c via the pump assembly? Grasping straws - surely not as h is one end and c is the other so any transfer accross the pump motor zone blows the pump - unless you guys know otherwise!]
 
Hi Shaun
To be honest I quite agree, but its proving to be time consuming to trap the fault and at the very least I need an engineer with the right approach, not another float valve.
 
Is there a branch between the ballofix and the ball valve?
If so, where does it go to?
Hi Ian,
Why exactly do you ask? I am hoping you have a point here, in fact there is a mcw branch which tees off between the ballofix and the float.
It tees off between and then runs over at high level before it then drops to serve a Redring Powerstream electric shower. The connection has been in place like this for a decade without issues and the Redring only has a cw supply.
 
Hi Ian,
Why exactly do you ask? I am hoping you have a point here, in fact there is a mcw branch which tees off between the ballofix and the float.
It tees off between and then runs over at high level before it then drops to serve a Redring Powerstream electric shower. The connection has been in place like this for a decade without issues and the Redring only has a cw supply.

If, as you say the problem goes away when you turn off the ballofix then it follows that mains cold water entering the gravity system is the cause of the problem.
It also follows that the problem lies downstream of the ballofix. If the ball valve is not letting by then its obviously going somewhere else.
I was wondering if the feed to the sealed system filling loop was branched off after the ballofix, the filling loop was letting by, the gauge had stuck and the cylinder coil had failed. A long shot i know but stranger things have happened and 30 years is a good age for a cylinder. I've known them to fail well before that age.
Problems like this can be very hard to pin down but mains water is definately getting into the gravity fed side somehow and then backfeeding into the cws. Have a good look at that branch pipe again and see if there is anything else it feeds into.
Hope this helps.
Ian
 
Hi Ian,
Testing a potential solution... years earlier the original feed to the ensuite was gravity via a line teed off the side of the 18mm cw gravity feed at 1st ceiling level.
Later the Redring was introduced [at the time the pump was not in place] and no surprise the flow was inadequate so a separate mains feed was then introduced.
At this stage the gravity feed and the mains cw feed were linked via a ballofix isolator before the shower unit, thinking one day I will add a pump.
Problem may well prove to be that because the ballofix was first to isolate the gravity feed the mains pressure connection to the ballofix was then reverse flow. Over time it has been OK and unused [closed]. I did operate it a little while back [just to stop it seizing I thought] but now when I come to it today, it leaks at the slotted screw but only when its turned again.
Right now its removed and relevant connections are terminal capped leaving the mcw feeding the shower and removing the interface.
Hopefully, I will let you know that my issue has been fixed in a couple of days. Any way thanks for your question which may well have rattled the right chain.....
 
If I understand you:

You have a working spring loaded one way valve (a proper check valve, airtight, not a flap valve that is only ish) on the cold distributing pipe, so we can rule out problems with mixer taps backfeeding up the cold distributing pipe.

You have a similar valve on the cold feed to DHW cylinder, then that rules out split coil and mixer taps passing water back up the cold feed.

The water can now only get into the cylinder from the top: the vent and the fill valve. Since the vent is only allowing a few drops of water through, we can assume that is normal expansion of water and not a punctured coil or mixer issue causing backfeeding through the DHW cylinder and vent pipe.

At this point, either you have a very leaky roof, or the water is coming in through the ballcock, impossible as it may seem.

Do I understand correctly, Terry?

If so, at this point, use a 15mm blanking cap on the tap connector that normally goes onto the ballcock and, if the level of the water does not rise overnight, I'm right, as by capping the ballcock, you aren't affecting anything else. If the level still rises, I'm missing something.

Final thought: is the overflow shared with something else and the cistern is filling through the overflow?
 
I was wondering if the feed to the sealed system filling loop was branched off after the ballofix, the filling loop was letting by, the gauge had stuck and the cylinder coil had failed.

Ian. Agree with your thinking, but, if the one-way valves are working correctly and are proper spring-loaded check valves then I must respectfully disagree because the only way the water added to the cylinder could backfeed the cistern is through the open vent, and the OP tells us he has a cup under the vent and can prove this isn't happening.
 
Hi Ian,
Testing a potential solution... years earlier the original feed to the ensuite was gravity via a line teed off the side of the 18mm cw gravity feed at 1st ceiling level.
Later the Redring was introduced [at the time the pump was not in place] and no surprise the flow was inadequate so a separate mains feed was then introduced.
At this stage the gravity feed and the mains cw feed were linked via a ballofix isolator before the shower unit, thinking one day I will add a pump.
Problem may well prove to be that because the ballofix was first to isolate the gravity feed the mains pressure connection to the ballofix was then reverse flow. Over time it has been OK and unused [closed]. I did operate it a little while back [just to stop it seizing I thought] but now when I come to it today, it leaks at the slotted screw but only when its turned again.
Right now its removed and relevant connections are terminal capped leaving the mcw feeding the shower and removing the interface.
Hopefully, I will let you know that my issue has been fixed in a couple of days. Any way thanks for your question which may well have rattled the right chain...
Ian. Agree with your thinking, but, if the one-way valves are working correctly and are proper spring-loaded check valves then I must respectfully disagree because the only way the water added to the cylinder could backfeed the cistern is through the open vent, and the OP tells us he has a cup under the vent and can prove this isn't happening.
Ian. Agree with your thinking, but, if the one-way valves are working correctly and are proper spring-loaded check valves then I must respectfully disagree because the only way the water added to the cylinder could backfeed the cistern is through the open vent, and the OP tells us he has a cup under the vent and can prove this isn't happening.

Ric, i know exactly what you're saying and that was rattling round in my head as i wrote my reply to Terry but we don't know for sure what kind of check valves are fitted. As you'll know some have quite a high opening pressure and if fitted next to the cws then you'd have zero or very little flow to begin with. On that basis i was assuming that he'd fitted the old swing check valves that we used on old CH systems to stop gravity circulation through the rads when in HW mode. As you said they don't completely seal off especially if they're installed horizontally which would most certainly allow any mains pressure water to get past. The way i see it is this; when he turns off a ballofix on a mains pipe the problem stops. Having replaced the ball valve 4 or 5 times we can rule that out, can't see it filling through the overflow as there's no F&E tank, next to nowt coming from the vent pipe so short of a hole in the roof it just leaves the outlets. Difficult one this as nothing adds up and its never easy solving problems via a keyboard. I'd love to be able to go sort it but i'm recovering from a broken back which is half the reason i'm on here, gives me something to do to relieve the boredom.
 
I think, having read through this thread, you need to get a Plumber/Heating Engineer in to look it over.

There are a few things that don't sound right. It may just be the terminology that you are using Terry but for safety's sake, I would advise you get someone in.
 
As you'll know some have quite a high opening pressure and if fitted next to the cws then you'd have zero or very little flow to begin with.
That was what raised my concern that he may have fitted swing valves and not proper check valves that would actually prevent backflow, rather than just slow it down a little. In my experience, single check valves aren't much use when the taps served by the check valve are less than two floors below the cistern, so a friendly merchant may well have supplied swing valves instead.
At this stage the gravity feed and the mains cw feed were linked via a ballofix isolator before the shower unit, thinking one day I will add a pump.
Problem may well prove to be that because the ballofix was first to isolate the gravity feed the mains pressure connection to the ballofix was then reverse flow. Over time it has been OK and unused [closed]
Thanks for highlighting that again, Ian. This is a matter of concern as to what dead legs may be present and also how the mains is protected from contamination. It may also be the cause of the problem, as a directional isolation valve may well not seal properly if the flow direction is reversed. I had originally read this section as meaning something completely different from what the OP has actually written, so I'm glad you've quoted it, thus forcing me to read it again.
Now I'm inclined to agree with Harvest: unless the OP can supply a diagram of the system, it's now sounding too weird to be solved by keyboard.

 
SOLVED!
A ballofix 1st installed to allow isolation of a gravity feed, then years later connected in reverse to mains pressure to avoid a capped tail and allow use of mains or gravity was caused to fail under the mains pressure leading to a mains water backfeed via the ballofix to the header tank.
Big thanks to all contributors especially Ian10261 who asked the question leading me to check out the failed component.
 
Help me get my head around this, please. So the mains supply pressure was pushing water backwards through the Ballofix and into the low pressure cold pipe?
Can you explain how this was able to backfeed the cistern via the one-way valves? Are we correct that the one-way valves are letting by in reverse direction?
 
This just gets stranger and stranger!
Isolating valves and non return valves not working.
 
That wasn't how I meant you to feel, so apologies if that's how I've come across.
All I meant was that that I thought your comment suggested that you'd only just seen the bit about the one-way valves not being one way and the isolator not isolating and hence the thread was becoming 'stranger and stranger' and I wondered if you'd read the thread in its entirity.
 
I've followed it from the start, perhaps not fully understanding it all but none the less puzzled considering all the valves in place and their functions. Well aware of strong and weak non return valves I might add.
 

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