Draining a Morco D61E water heater

[blackrose]

I'm trying to drain my gas water heater. After depressurising the system and isolating the cold water feed I  took the drain screw out but only a drop of water came out of the hole. I was expecting a bit more. Is there another screw I need to remove to release any vacuum that's holding residual water in place inside the heater?

 

Sorry the picture has uploaded upside down.

 

[MoominPapa]

Yes, and no. Turn a hot tap on to provide a second path into the system. On my installation this very conveniently lets air in via the drain plug hole and the water exits via the tap.You may  not be so lucky.

 

MP.

[blackrose]

That may be what's happening on mine, I'm not sure. I've got a few more drops coming out now and some out of the tap. 

 

I guess in the event of a freeze up, as long as I leave the drain screw out and taps open so expanding water can escape they'll be no damage? 

[rusty69]

20 minutes ago, blackrose said:

That may be what's happening on mine, I'm not sure. I've got a few more drops coming out now and some out of the tap. 

 

I guess in the event of a freeze up, as long as I leave the drain screw out and taps open so expanding water can escape they'll be no damage? 

 

 

I thought exactly the same thing when I disconnected the two ends from my solar water panel one year.  Granted, it was outside, but the water left inside froze over winter and split the coil in various places.

[blackrose]

17 minutes ago, rusty69 said:

 

 

I thought exactly the same thing when I disconnected the two ends from my solar water panel one year.  Granted, it was outside, but the water left inside froze over winter and split the coil in various places.

 

Oh dear, that's not good.

 

Water has been dripping out the hot tap on my kitchen sink for half an hour so it's got to be coming from somewhere...

[Alan de Enfield]

Water tends to freeze 'from the outside inwards'

 

So if you have a few inches of water in (say) a bend then the water will freeze at the 'ends' of the slug of water, and along the 'sides' where the water touches the pipe, and then gradually work 'inwards'.

 

This means that the water forms an ice plug at each end which, as the water 'inside' the slug freezes and expands it has nowhere to go except to split the pipe.

Edited December 2, 2022 by Alan de Enfield

[BEngo]

Turn a cold tap on too, if nowt happens,  blow into the cold tap.

That empties mine, but your pipework will be different.......

 

N

 

 

[Arthur Marshall]

Just leave all taps on the boat open, including the cold, drop the shower head to the floor to make sure that it drains. There's no stopcock between my pump and the tank, so any water in the pump on that level just drains back to the tank. I've not had any problems over winter yet, but I don't have an accumulator or anything complicated like that!

If the plumbing is plastic there's room for a bit of expansion even if it does freeze a bit of residual water, so it's unlikely to split unless there's loads in there,  which there won't be. And with the taps open, it can expand along the pipes, anyway.

Even if the pipes split, that's a cheap and easy repair. It's the Morco that you need to be sure of.

 

Edited December 2, 2022 by Arthur Marshall

[MoominPapa]

2 hours ago, Arthur Marshall said:

drop the shower head to the floor to make sure that it drains.

 

This can be  dangerous advice, at least one boat I know did this and the water tank emptied slowly, by gravity, into the shower tray, overflowed and filled the bilges. Twice, before the owners worked out what was going on.

 

MP.

[Arthur Marshall]

32 minutes ago, MoominPapa said:

This can be  dangerous advice, at least one boat I know did this and the water tank emptied slowly, by gravity, into the shower tray, overflowed and filled the bilges. Twice, before the owners worked out what was going on.

 

Never thought of that. The water would still have to rise a metre up to the shower tap level though, before it could come down again. In my plumbing, anyway, so I think I'm safe, but I can see the danger. Glad you pointed it out.

[Stilllearning]

Some water systems have an air valve fitted, so an air pump can blow all the water out for winterising a system.

[MoominPapa]

3 hours ago, Arthur Marshall said:

Never thought of that. The water would still have to rise a metre up to the shower tap level though, before it could come down again. In my plumbing, anyway, so I think I'm safe, but I can see the danger. Glad you pointed it out.

If the shower head is lower than the water level in the tank the water can siphon out.

 

MP.

[Ex Brummie]

The cold inlet to the heat exchanger is lower than the hot supply pipe, so you need to relieve the cold supply, I open all the taps, hot and cold plus the shower, then I disconnect the cold supply pipe. Have a towel or bowl beneath the joint to catch the water. I then reconnect the pipework so that when I recommission it all i have to do is start the pump and and close the taps as they start to flow.

[blackrose]

11 hours ago, Arthur Marshall said:

Just leave all taps on the boat open, including the cold, drop the shower head to the floor to make sure that it drains. There's no stopcock between my pump and the tank, so any water in the pump on that level just drains back to the tank. I've not had any problems over winter yet, but I don't have an accumulator or anything complicated like that!

If the plumbing is plastic there's room for a bit of expansion even if it does freeze a bit of residual water, so it's unlikely to split unless there's loads in there,  which there won't be. And with the taps open, it can expand along the pipes, anyway.

Even if the pipes split, that's a cheap and easy repair. It's the Morco that you need to be sure of.

 

 

Yes but we're not talking about draining the freshwater system here, the question was specifically about draining the water heater which unlike plastic pipes is particularly susceptible to frost damage.