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Is anyone familiar with the Jet Range isolation valve DN20 which is operated by screwdriver? Does this valve have a known design fault causing it to fail?

During the retification of the leak in my other thread "Wear And Tear Causing Leaks?" (in another part of the system), the plumber approached this valve behind the boiler intending to switch off the mains cold water supply to the system in question. In doing so he removed the pipe insulation close to this valve so he could access the screwdriver slot. To his amazement, as a result of removing the insulation, the copper pipe popped out of one end of the valve before he was able to apply the screwdriver. Mains water pressure spurted out, causing the plumber to have to stop the 20mm flow with his thumb. He was alone at the time!

Some time later, I walked past the builing and heard a shout for help. It turned out that I could not help by turning off the mains water immediately because there was no other isolation valve in the area. I had to drive half a mile to the water meter at the entrance to my property to turn off the water at the meter there.

Anyway, although the plumber commented at the time that this valve was known to have a faulty design and was no longer on sale as a result, he wants to charge me for a new valve of a different type and for his time because the original valve was by now out of warranty. Is this fair?
 
any pics of the valve ?
 
This is the valve in question.

IMG_20190428_170740.jpg
 
thats not a valve its a non return or check valve eg

Pegler Yorkshire -

and it would fail if its not installed correctly eg not tight enough
 
On your Pegler example, how does the copper tube connect to the valve? Is it the same as my photo in that the tube appears to be just inserted into the plain end then tightened?

IMG_20190428_172859.jpg
 
yea normally a brass olive in the bottom
 
So, would it suggest that the installation of this valve was not fully tightened?

yes or mis installed eg not fully in or missing an olive etc or not installing a liner inside the alk pipe

doesnt let go for no reason if its the fittings fault i would expect to see the collar to pop / threads to fail etc
 
yes or mis installed eg not fully in or missing an olive etc or not installing a liner inside the alk pipe

doesnt let go for no reason if its the fittings fault i would expect to see the collar to pop / threads to fail etc
Or the engineer the other day did something wrong whilst there.
 
I’m not even sure that’s an isolators with the screw driver slot? Isn’t it just a means of checking the NRV is working?
 
ShaunCorbs, You mention alkathene pipe. I am talking about copper pipe.

Is my valve in question suitable for use with copper pipe? Could that have been the problem?
 
Dn is normally the dia of the pipe eg dn22 for 22mm tube

What size pipe was it fitted on ?
 
The valve is marked DN20. The inside diameter of the plain holes each end are 20mm, maybe 21mm. Don't know the size of the copper pipe each end without going and trying to measure it.
 
Last edited:
Copper tubing - Wikipedia

"In the plumbing trade the size of copper tubing is measured by its outside diameter in millimetres. Common sizes are 15 mm and 22 mm. Other sizes include 18 mm, 28 mm, 35 mm, 42 mm, 54 mm, 66.7 mm, 76.1 mm, and 108 mm outside diameters."

So how does 20mm fit in this scenario?
 
Would need a pic
 
Where it was installed
 
That’s 22mm pipe so I would say not the parts fault the installers at fault

With it being 20mm it’s for alk eg watermains etc

What’s with the two flexis ?
 
So, are you saying that the installer is at fault for using a valve designed for use with 20mm alkathene on a 22mm copper installation?

I am guessing that the two flexibles pipes were used as an easy method of connecting the copper sections together? Looks rather Heath-Robinson to me.
 
Correct it won’t fit as you’ve measured the hole is 20mm so must of been rammed in or something

Them flexis arnt rated for heating so best get them replaced
 
Trevor,

DN20 is an ISO sized fitting for 3/4 inch pipe (26.66mm). It is not intended to be used with 22mm pipe. With respect to copper pipe it is intended for 3/4 inch outside diameter.

Normally if metric and imperial fittings are mixed up with 15mm and 1/2inch diameter pipe they generally work (not always). However the size difference between 22mm and 3/4inch is too great for success to be a possibility.

This would account for the pipe “popping” out - but I would be surprised that the pipe remained in place and leak free since the original installation - unless it had been “mumified” with ptfe tape!!

The Jet valve in question is a non return valve, the screw is for testing, it is not intended for isolation, there should be a proper (ball) isolation valve at the point of entry into the boiler house - the installer will have fitted one - he/she won’t have driven 1/2 mile to isolate the supply.

The flexibles look to be a makeshift filling loop. They should be replaced with the correct WRAS compliant ones.

If I were in your shoes, I would check out the system on a line by line basis, both for the design ( heat balance and flow calculations) and the specification of pipework and fittings / quality of installation work.
 
Trevor,

DN20 is an ISO sized fitting for 3/4 inch pipe (26.66mm). It is not intended to be used with 22mm pipe. With respect to copper pipe it is intended for 3/4 inch outside diameter.

Normally if metric and imperial fittings are mixed up with 15mm and 1/2inch diameter pipe they generally work (not always). However the size difference between 22mm and 3/4inch is too great for success to be a possibility.

This would account for the pipe “popping” out - but I would be surprised that the pipe remained in place and leak free since the original installation - unless it had been “mumified” with ptfe tape!!

The Jet valve in question is a non return valve, the screw is for testing, it is not intended for isolation, there should be a proper (ball) isolation valve at the point of entry into the boiler house - the installer will have fitted one - he/she won’t have driven 1/2 mile to isolate the supply.

The flexibles look to be a makeshift filling loop. They should be replaced with the correct WRAS compliant ones.

If I were in your shoes, I would check out the system on a line by line basis, both for the design ( heat balance and flow calculations) and the specification of pipework and fittings / quality of installation work.
So why could he not use a 3/4 olive?
 
All sorts at fault here.
Wrong size valve fitted to 22mm copper. ( but would probably seal)
Wrong flexi pipes used as a filling loop. .
Fitter that had the problem thinking the non return was a service valve. Which he then unscrewed the Center. This would then have popped out, causing the main flood.
Looks like the OP is looking for blame, it it’s just a case of bad installation and a mistake by the guy investigating.

Remedy.
Pay the last guy to fit an approved filling loop.
 
"Which he then unscrewed the Center".

That was not the case. Nothing was unscrewed, or even touched on the valve, prior to the potential flood. The plumber said he merely removed the insulation around the valve for access when the pipe popped out of the valve.

The "last guy" working for the original supplier/installer/service was very much part of this issue as in giving me wrong information, and also much to blame regarding my other thread on this forum today.
 
The Jet valve in question is a non return valve, the screw is for testing, it is not intended for isolation, there should be a proper (ball) isolation valve at the point of entry into the boiler house - the installer will have fitted one - he/she won’t have driven 1/2 mile to isolate the supply.

Apparently the installer did not fit an isolation valve because they claim that would contravene the regulations that state that an unimpeded flow of mains water needs to be constantly available to quench/flood any serious malfunction in the ETA biomass boiler. An isolation valve could be closed manually accidentally. Hence the need to drive half a mile to turn off the supply at the incoming water meter.
 
I have had a detailed conversation with Wolseley/Pipecentre who are the suppliers of this Jet double check valve known as DZR.

He said this valve is still sold as a current product and does not have a design fault. He said the valve comes with universal ends that are intended to be used on various pipes including 22mm copper pipe compression.

As the 22mm copper pipe popped out of one end of the valve under mains water pressure, he said that the failure was due to incorrect installation by the plumber.

Does all of that make sense?
 
I think you’d do well to drag an admittance of design flaw out of them. Unless there is a product recall I doubt they would be obliged to admit to anything.
 
That’s really neither here or there, I don’t tend to fit that brand so it’s kind of inconsequential. My point is though unless there is some product recall I think you would have to assume that even if it is of poor quality then the valve should be fit for purpose. Look at it this way I wouldn’t have thought that a company like wolsley would continue to sell a pipefittings known to have serious failure issues​
 
Trevor,
A couple of points. I have never seen a properly installed heating installation that cannot be isolated from all the external services ( compressed air, water, oil, gas, electricity et al) at the boundary limits to the boiler house) . It is basic safety that applies to any process. The fact that a service (ie water) needs an unimpeded supply, does not mean that it is not to be provided with a means of isolation for serving or maintenance. It does mean that isolation should be designed to prevent accidental isolation.

With respect to quenching - it is highly unlikely that a large domestic or small commercial wood fired, coal, coke, straw or biomass boiler has any form of quenching system. If you inject even a small quantity of water into an operating boiler (at 900 degrees plus), you will probably get an explosion. As and when you get a tube leak in your boiler - as it ages, look inside to see the damage even a small amount of water entering through a pin pick hole causes. Some boilers have steam injection, but they are generally related to power generation facilities.

In an emergency situation a biomass boiler is controlled by:
venting steam whilst increasing the flow, reducing combustion air, whilst maintaining cooling air to the burners and shutting off the fuel source. Having said that, the majority of fire incidents occur downstream of the boiler in the storage area ( biomass chips have a tendency to self combust if stored incorrectly).

Your boiler may have an external fire protection system, but even that is uncommon in the boiler house of a large domestic / small commercial biomass boiler.

Apologies for the soliloquy - but any boiler and particularly a biomass boiler burning a variable fuel source should be maintained by someone who is fully conversant with how the boiler operates. If the boiler is set up and operated incorrectly, you will get slagging, that produces hot spots and the integrity ( and life) of the boiler will be compromised.

As for having someone tinkering with the system who cannot fit a compression joint - I would show him the door.
 
Thanks for your observations Brambles. Only the biomass boiler supplier/installer/servicer company have had anything to do with the system. The plumber in question works for them. The boiler is a ETA Hack 70.
 

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There's nothing wrong with that NRV.
It's suitable for both bsp 3/4, (DN20) using the external thread and 22mm with olive internally.

I've used hundreds of Jet fittings of that type.

The 22mm pipe wasn't pushed in far enough and or not tightened correctly.
If the 22mm pipe was available for inspection it would show the mark where the olive gripped, or failed to grip.

And there should be a mains cold isolation valve nearby, whether the boiler has quenching or not, for exactly the situation that happened.
The quenching is to stop fire if it's burning back into the fuel feed tube or fuel store, not to extinguish the fire withing the combustion chamber.

The flexis are on the filling loop so should be O.K as it's normally isolated.
 

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