[Nick_Thompson]

What is that little threaded brass thingamajig on the bottom of these heaters?

Nick

[slap bash]

Its a drain remove and the heat exchange will drain  which you should do on freezing nights and days so the water in the system will not freeze,expand and crack heat exchanger or the pressure valve.

[dazmond]

drain screw.

a little tip.when you ve finished for the day when using the heater(before you reel in your hose fully)turn your pump off and open your pole tap up and let all the water/pressure drain out while your reeling in.that way you wont have loads of pressure in the heater when unscrewing the drain screw.there should only be a little dribble left in it then.

if you dont do as above and unscrew the drain screw without opening up your pole tap with the pump off  itll spew out water everywhere with the pressure.

[Nick_Thompson]

Thanks guys, but how does it unscrew? It just seems to be a brass threaded tube.

Nick

[Dave Willis]

It's also a pressure relief valve (adjustable). Quite flimsy too so don't try mole grips on it. If you look inside the tube you can spot the adjusting screw.
I have my pump after the heater hence no pressure at all in the unit. I personally never drain mine I just protect from frost.

[dazmond]

Thanks guys, but how does it unscrew? It just seems to be a brass threaded tube.

Nick

is this a trick question nick?

you turn it a few times and water will drip out of it.

[Nick_Thompson]

Thanks again chaps!

And, no, I am serious dazmond, honestly.

So, I take it that the outer body of the tube unscrews, and as Dave pointed out, this procedure is to be carried out carefully... no mole grips.

It does look rather inaccessible. What tool are you guys using? Snip-nose pliers, perhaps?

Dave, are you experiencing any problems with the pump's diaphragm, having the heated water passing through it like that?

Nick

[Dave Willis]

No problems with the pump - last time I looked it up it was well within the temperature range. I don't know anyone else who sets their system the way I do it but it makes perfect sense to me.
The drain plug should protrude about a cm out of the casing and should be finger tight ....... unless we are looking at something else  

[Nick_Thompson]

The drain plug should protrude about a cm out of the casing and should be finger tight ....... unless we are looking at something else  

I'm going to have a better look at it tomorrow, but as you can just about make out in the picture, this fitting is actually recessed a little to lie just beneath the outer casing.

Oh, and by the way, I do appreciate the input guys; it's very reassuring to know that these mutual conversations we share on calefaction are by no means restricted to our purified water only, nay, such warmth of feeling and concern is oftentimes so readily poured out as to cause a produce of a little warm water myself... from my eye!

Thanks

Nick