Plumbing questions please.

[frank rabbets]

1. The expansion vessel failed in my c/h boiler as evidenced by wild fluctuation of the pressure needle with temperature. Question is, where has all the air gone? I decided to depresurrise the system and fill the expansion vessel with air through the schrader valve to get the boiler reliable for a bit. I could hear air bubbling through the pipes proving that the diaphragm in the expansion vessel had failed. Needle fairly constant.

2. Is it OK to use the cold type on/off valve for hot water supply? The gate valves with the red knob always seem to dribble.

Thanks.

 

[Andy]

Expansion vessels often loose pressure, if the air side has no water in it ie none comes out of the schraeder valve, drop the water by opening drain valve & leaving it open ( if a combi boiler isolate at the valves underneath).
Pump up with a foot pump to about 1bar, close drain cock, repressurise water side to about 1 bar cold.
This is for an average sizes system, if you are in a larger property , the pressures will be different.
If there is water at the shraedervalve, new vessel required as the diaphragm has perforated.

They can loose pressure through the valve, or the internal diaphragm.

If you mean lever type valves on the hot, yes that’s fine, if you mean stopcock with a washer, on a gravity tank fed system, no as sometimes there isn’t enough pressure to lift the jumper, on a mains pressure hot water system, levers are good
Andy

 

[Andy]

Ps, i read your post again, the diampram has only failed if water comes out of the valve on the air side of the vessel

 

[StarCruiser]

Is the pressure vessel in the back of the boiler? If so, and it’s gone, it can be easier to add one external to the boiler.
Care must be taken not to leave the boiler isolated on its valves.

 

[frank rabbets]

Thanks Andy and SC. Used to be gravity fed till I ripped it all out and fitted c/h and a Worcester combi boiler 10 years ago. Plenty of pressure to lift the valve seal. Been racking my brains for years over that reasoning. I used 500 feet of pipe most of it by crawling under the floor boards and 10 rads so I might fit a remote and larger expansion vessel. Looks impossible to get the EV out of the boiler to replace but I might be able to remove the pipe of it and blank it in case it starts leaking. Any thoughts on thread?

 

[StarCruiser]

Not sure about the Worcester Bosch but if it’s confirmed that the bladder has gone (as Andy said water out the Schrader valve) then it would probably involve almost complete disassembly of the boiler.

Thread size, I would guess (and it is a guess) possibly a metric thread (as it’s German) something like 16mm across. I would guess Andy might have a better idea on that.

 

[Andy]

Probably 3/8 bsp, as sc said, fit a remote ex vessel, those bloody Worcesters often require removal of the boiler from the wall to change the ex vessel & or prv.
It shouldn’t leak if you do leave it connected, & some of them are only connected by a flexi pipe.......real crap design
I refuse to fit Worcesters! They can be such a pain to maintain, the best thing about them is their marketing

 

[StarCruiser]

I was thinking 3/8 BSP before dismissing that for the metric theory.

What’s your preferred boiler Andy? Lots seem to be going for Veissmann.

 

[Towpack]

We’ve booked a system flush for later this month. We have a Myson kickspace heater in the kitchen which stopped blowing hot air a few weeks ago and it turned out one of the flexible hoses connecting it to the copper pipe system was blocked solid with black gunge. So bad in fact that it was impossible to unblock so fitted two new hoses with shut off taps to make future disconnection/replacement easier. The rest of the system is working fine. We have a pressure vessel separate to the boiler, linked to the cold water system to top up the pressure periodically.

 

[Andy]

rich ,
viessmann are good now they have got rid of the thin rubber hoses connecting the heat exchanger,! fitted over 140 boilers last year, ( not contract / social housing jobs) mostly glowworm which are basically the same as Vailant, ( same factory) 7 yr std manuf warranty & we’ve had very very few issues.

Worcesters we find are generally quite reliable for the first few years, but when they go wrong, parts can be a real bitch to replace. As I said their marketing is brilliant,they are known for this throughout the advertising / marketing industry

 

[StarCruiser]

My cousin’s husband has worked for or on Vaillant boilers for as long as I’ve known him. Rates them very highly.

I didn’t think much of their unvented cylinder. Lovely design except you could pull the access panel off with one finger or a child could do it exposing live metal unshrouded terminals.

 

[StarCruiser]

We’ve booked a system flush for later this month. We have a Myson kickspace heater in the kitchen which stopped blowing hot air a few weeks ago and it turned out one of the flexible hoses connecting it to the copper pipe system was blocked solid with black gunge. So bad in fact that it was impossible to unblock so fitted two new hoses with shut off taps to make future disconnection/replacement easier. The rest of the system is working fine. We have a pressure vessel separate to the boiler, linked to the cold water system to top up the pressure periodically.

was this on a former open system converted to sealed TP? Just trying to fathom why the black gunge.

 

[Towpack]

It was converted to a closed pressurised system from an open, gravity fed system several years ago with a new boiler and quite a bit of pipe work alteration. The black stuff is system corrosion, supposedly, yet clean water comes out of the system when bleeding rads etc. Sludge usually collects in the bottom of rads but thermal imaging of them shows quite uniform temp so there can’t be that much in there. The flexi pipes to the Myson are around 10mm ID so more prone to blockage maybe? A pressurised system flush and the adding of some inhibitor is just playing safe really.

 

[StarCruiser]

That’ll be why the black sludge then, being previously an open system with an amount of oxygen entering the water at the header tank.

 

[frank rabbets]

The Worcester has been perfectly reliable apart from the EV. I must admit that I've never had the boiler serviced. On a scale of 1-10 how serious is this Andy? I have however flushed the system regularly and put that expensive inhibitor in.

 

[StarCruiser]

You’re better off leaving the water in the system Frank. New water = New oxygen which has to be used up creating corrosion, albeit minor. Plus you’re throwing away that expensive inhibitor each time.

 

[Trevor]

I’ve just had a Grant oil combi fitted and to get the warranty a magnetic sludge catching thing had to be fitted as well. I have to clean it out every 6 months. Quite clever that you can isolate it to remove the bit to clean so no drain down involved.

 

[IRLGW]

Guys, I spent all morning going over my truck looking for the expansion tank but cannot seem to find it, in fact I didn't even know it was a Toyota part! its not in the FSM either? Am I on the wrong forum?

 

[StarCruiser]

I’ve just had a Grant oil combi fitted and to get the warranty a magnetic sludge catching thing had to be fitted as well. I have to clean it out every 6 months. Quite clever that you can isolate it to remove the bit to clean so no drain down involved.

I’ve seen those they look brilliant. I’m not surprised on the requirement if it’s an existing system.