Any plumbers about!? Franke Minerva tap

[Grobag]

Quick query, got a Franke Minerva boiling tap and water has started flowing through the tundish. The manual says it's a pressure release, and blows if the pressure exceeds 5 bar. It's fitted with a pressure reducing valve on the incoming supply so I'm assuming it isn't due to high mains pressure. The bit I'm confused about is its boiling water running through the tundish, and the cold feed pipe between the tank and the tundish is also hot. Anybody got any ideas on why boiling water would go against the flow and reach the tundish? Thanks.

[LookAtMyCat]

I'm not familiar with that particular product but under-sink unvented systems use the incoming cold supply as the expansion. Ones i've fitted state a minimum length of cold inlet after an isolator of a certain diameter (eg: 4m of 22mm, 7.5 of 15mm) with a PRV (usually set at 6bar) in that cold pipework. You haven't introduced any new isolation or check valves etc into the incoming cold system? If it's expanding a lot then you will get hot back to the PRV but it's right in that it would go against the flow.

I would go back to your installer who will likely be familiar with it. Logic says that it is either the expansion room is reduced for some reason, or the pressure reducing valve is borked. Honeywell do an adjustable one with an integral gauge for about £25.

[Grobag]

Thanks for the reply. No new isolation has been introduced since it was installed. I turned it all off to let it cool then did a filter change. Turned the water back on but not the heater on yet as water is flowing through the tundish again. Not sure how the release valve works but I would have thought that once the pressure is released the valve would re-seat and be good to go again? Think for the time being I'll isolate it and call the installer!

[Gingerbread Man]

If water is flowing out of the pressure relief valve when cold, that would indicate it's tripped because of pressure typically. Some PRV's let by once used, but typically a drip, like a dripping tap. If it's flowing through, it's opened up to allow it to do so.

[Grobag]

Thanks. Yep as soon as the cold is turned back on it flows through the tundish which I assume means either the pressure release valve is a one-hit wonder or its somehow got stuck open. Either way it sounds like a replacement is needed, I'll get a plumber to take a look. Thanks for your help.

[Richie Slow]

If you need to replace it have a look at the Insinkerator ISE3N1 tap. It will save you a good wedge of cash and is an all-round better product than the Minerva (in my opinion).

We don't supply Minervas any more

[Grobag]

Thanks for the heads-up Richie. Spoke to the plumber, he reckons that its just scale caught under the seat of the pressure relief valve, as it should close automatically once any pressure build-up has been released. So hopefully just a bit of TLC to the valve should sort it rather than a whole new tap!

[Grobag]

A conclusion to close what was always gonna be a fairly dull thread! Turns out it was a faulty pressure release valve, the seating that the washer sits on was incomplete and after a while the sharp edges lunched the washer.

Not sure why it was hot rather than cold water that was coming out, can only think that the tank pressure was higher than the pressure that the reducing valve was set to. Still, no worries, a new valve appears to have sorted it, so another job off the list!

Thanks to those that replied.

[MichaelG77]

Hello,
I know it was a long time ago, but I have the same problem. May I send you a picture of my instalation so that you can show me which part you replaced to fix it? Unfortunately, I do not know the correct name of these parts.
Thank You
Michael