Header overflow - should be so simple.

[Terry Godber]

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?

 

[ShaunCorbs]

Backing up through the cold feed check in the morning is the tank water inside the tank warm / hot

 

[Terry Godber]

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!!

 

[Terry Godber]

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!

 

[ShaunCorbs]

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

 

[Ian10261]

Is there a branch between the ballofix and the ball valve?
If so, where does it go to?

 

[Ric2013]

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?

 

[Terry Godber]

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!]

 

[Terry Godber]

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.

 

[rpm]

No transfer across the pump so rule that out.