I'm trying to drain my Duetto IV steam boiler.

I have raised the machine and placed a large dish under it.

I undid the hand screw under the (cold) steam boiler and have removed it.

All I'm getting is a very slow drip drip drip of what basically looks like chalk water. I popped the top open and the vacuum valve is moving freely so I think it can let air in at the top and there is no vaccum lock? Opening the water valve did nothing on the rate of dripping.

I also popped in a small allen key into the hole to see if something was blocking it - it want up an inch or two without any obvious resistance and then feels like it hits something solid. I didn't want to roce it in case it's something structural.

Should I be using a wrench to undo the hex nut? Or is there some other reason why I'm only getting a drip rather than a drain? Maybe I've scaled it up so bad because of not flushing when I didn't realise you had to do that?

Thanks in advance for any thoughts.

I've been using nothing but bottled Tesco Ashbeck water which is 80mg/l tds. However, I have spent a year drawing nothing but steam from the steam boiler as I didn't realise you need to flush it....

The boiler was definitely full and steaming properly from a 100% correctly functioning machine this morning.

So you think I've done everything I need to to get water to come out? In which case it really is scaled up pretty bad?

[Edit: Also perceived wisdom seems to be 14-28g of citric acid per litre of water. Do you agree? Or is there enough evidence in my case to use something stronger?]

f full pressure flow does not come out of the hot water spigot at operating temperature,

This happens - the machine is operating 100% correctly.

However, when opening the drain plug on the steam boiler it drips very slowly - 3h in it's still dripping. This is not the case for the brew boiler - there opening the drain plug and lifting the lever makes water come out at a healthy pace.

I did try putting the hot water arm in my mouth and blowing - I was able to close the vacuum valve and then the increase in pressure made the drips from the drain plug go a bit faster but not a lot.

So it sounds fairly bunged up.

Just for reference, in case anyone hasn't read Jim Schulman's FAQ:

Generally, a flush through descaler uses about .5 to .75 fluid ounces (1 to 1.5 tablespoons, or 8 to 12 grams) of citric or tartaric (grape) acid powder dissolved in 1 liter of water. This is a 2.25% to 3.5% solution, equivalent to 33% to 50% dilute lemon juice. Cleancaf and other coffee manufacturers' descalers use this formula. Theoretically, these amounts will dissolve about 12 to 18 grams of scale per liter, but that would require leaving the solution in for several days; in practice, it is used for an hour or two to dissolve up to 5 grams of scale.

I'll give that a go and hope it clears up. Thanks for your help BaristaBoy.

Just for future reference if anyone stumbles on this...

Indeed descaling with 13g/l Citric Acid solution freed this right up.

Man does having boiler drains and an independent steam boiler switch on the Duetto make life easy when descaling.