Cause & effect (funny story)

[Radian]

This maybe isn't so much about asking for advice as giving it

I had a leaking HW cylinder (23 years old) that I got fed up patching up with plumbers gold - so decided to replace it and do some remodelling of the plumbing in the airing cupboard while it was all pulled out.

before, during, & after:

Apart from the new cylinder I converted from Y plan to S plan and finally got round to connecting up a single UFH zone that has been waiting to be finished since our house extension was built last year

Everything seemed to go well with leak free solder joints and just one easily fixed weeping compression. However, on waking up the following morning after the big switch-on, I sensed a damp smell coming from the dining room. On investigation; holy xxxx!!! There's water running down the walls and leaking bulges in the plasterboard ceiling!!!

Now the advice might seem to be: leave this kind of work to the professionals! It did briefly cross my mind, but this wasn't the first time the dining room ceiling was in need of repair due to a plumbing catastrophe - and that was down to the 'professionals' who installed the central heating in our brand new house. Twice in fact.

The usual flurry of drain-down activity then took place and not knowing what bit had gone wrong, I turned off the water main and emptied all the storage tanks just to be sure. Then came the unexpectedly difficult task of finding the source of the problem. None of the recent pipework was leaking, despite the airing cupboard being directly above the dining room. But the big leak was somewhat further down the room - more like below where the bathroom was.

What had I done in there I wondered? The only thing I could think of was that I had emptied lots of water from the storage tanks via the bath taps when I did the work - oh no! Was the bath waste leaking (it never gets much use as everyone here prefers a separate shower) in which case I just released a load of water again in my panic drain down! But then why didn't I notice this before?

The only way to check was to remove the tiled-over bath panel and inspect. Also not easy because the waste was under the chipboard floor and difficult to get at. Fortunately my Aldi gooseneck inspection camera toy came to the rescue and revealed no problem with the waste. But it also revealed two pipes for some upstairs radiators spanning the entire region that was leaking below.

So what if something I did upset a joint in this area? How the heck would I be able to examine pipes running beneath the chipboard flooring underneath a bath? Just too painful to contemplate. Instead I went down to the dining room below and, for the camera, drilled an 8mm hole in the ceiling that seemed to be the epicentre of the leak (figuring it would all need repair anyway if I had to re-pipe from below). However what I found looking in here was not at all what I expected:

Spoiler: Not my fault after all

The camera revealed a 20mm overflow pipe from the bathroom toilet cistern crossing through slots in the floor joists was impaled by a ring shank flooring nail. It had been sat waiting there for 23 years before getting its big moment:

Presumably the cistern fill valve got cruded-up as a result of disturbing sediment when I did the initial drain-downs. Flushing the toilet that evening started a steady flow that had never adequately been put to the test by the folks that built this place Rather than attempt a difficult repair I've now opted for a syphon with overflow-to-bowl and capped off the booby-trap for good.

So my advice is not to assume the obvious when it comes to effects and their causes.

 

[ShaunCorbs]

we’ve all been there, think feck what have I done to cause that much water

What actuators are they ?

 

[Ric2013]

Pipework is tidy!
12345678

 

[Chuck]

You might want to consider adding a few pipe supports. (Imagine a kid deciding it would be fun to pull on the AAV . . .)

 

[Radian]

we’ve all been there, think feck what have I done to cause that much water

What actuators are they ?

Well, the valve body's are Drayton 2-port. As for the Actuators they are 6V micromotors with 298:1 step-down gears. I have a pathological dislike of typical sync. motor actuators & their phenomenally crappy design

Configured as servos these little motors can change valve position in under one second, for less than 1W. But they can also be used to modulate the valves. I have a Raspberry Pi controlling them with constant-current H-bridge drivers using my own software regime.

One thing I have been able to do is use the modulation to work-around a serious problem that I had with the single zone UFH: This only loads our boiler (Flexicom 30hx) with around 2kw so there was way too much on/off cycling if ever run alone. These old boilers only go down 3:1 so 10kw is the minimum it can do efficiently. My fix relies on the observation that the demand for UFH generally overlaps with the rest of the house and the total losses are such that opening the radiators zone enough to keep the boiler firing (at its lowest rate) just keeps the rooms ticking over even when not actually calling for heat.

It's actually worked very well, as the temperature in most rooms is now noticeably more constant. The excess 8kw is easily absorbed through our 20 radiators without driving temperatures over the TRV settings. The central thermostat just puts out a demand for the radiators zone a little less frequently. It might be different in the spring/autumn but the UFH zone is in a garden room that gets a terrific amount of solar gain so heating is only required there when the rest of the house is already being heated.

Pipework is tidy!
12345678

Thanks! I do quite a lot of different types of metal bashing and I like soldering, brazing and welding so working with copper is always a treat.

You might want to consider adding a few pipe supports. (Imagine a kid deciding it would be fun to pull on the AAV . . .)

Funny you should mention that... I've got some 10mm threaded rod & brass munsen rings to support the whole rig but I've been a bit distracted trying to diagnose Water exchange in F&E tank via feed pipe to system. Thanks for reminding me to finish it off!

 

[Last Plumber]

Actuators they are 6V micromotors with 298:1 step-down gears.

Where are they from?
Who makes those?
I take it there is no auxiliary switching from them?

 

[Radian]

They came from Pimoroni They supply Raspberry Pi computers and all kinds of other electronics. No there's no switches attached but if you were rolling your own actuators and required that function then a micro-switch could quite easily be placed somewhere near the shaft coupling.

There is also an option to buy a sensor board that fits on the back shaft of the motor. This encodes the shaft position so can be used to keep track of the rotation in software. I don't use this myself because I have set the motor driver to provide a maximum of 350ma which allows the motors to safely stall at the end-stops. The driver does this by rapidly mark-spacing the output to limit the voltage in the motor winding to around 2.6V

At the end-stop positions the power dissipated is therefore just 0.9 Watt (contrast that with the standard actuators - the last one I used was around 6 Watts dissipated in the stall resistor and sync. motor). And the torque multiplication of the gearbox means that the valve actually stays in place with no power at all when the valve is open. Only when closing do I need to keep the motor stalled to completely shut off the valve otherwise there is a small amount of backlash that results in a tiny bit of flow. Just to save even more power, I remove the stalls whenever the circulating pump is off.