Head Boom

[Grehan]

Folk here seem to like lavatory questions, so here's mine.

1. Use the head (Lavac). Pump into the holding tank.
2. Brief silence, then muffled boom, then another. Sometimes another a little while after.
3. Head seems to operate ok. Tank seems to empty a.o.k.

So why the noise? - which sounds like the metal tank flexing and sounding. I thought it might be lack of breather outflow (as it were) but can't see anything obvious.

Any notions? e.g Do they all do it? Is this a terminally dangerous condition?

BTW
Is it head, or heads?
I have an idea the word is from Beakhead therefore head. But people seem to refer to the room (cupboard?) as the headS.

 

[chrisc]

have the same thing on my boat ,i put it down to very thin stainless used in the tank manufacture,mine is made in US. I have thought of putting a heavy (lead)
patch on it to dampen movement . but I don't think there is any danger of damage to the tank from this,

 

[Guest]

Grehan
I can think of three possible reasons for the noise:

1- increasing air pressure inside the tank as it is filled due to a blocked vent - unlikely, but easily checked (suck it and see, as they say).

2- thermal contraction of the metal panels causing them to flex due to introduction of cold waste liquid into warm tank - also unlikely, but possible.

3- increase hydrostatic pressure inside tank as it fills with new liquid, causing tank walls/floor to flex outward - most likely cause.

If noise is disturbing (eg to sleeping crew), I suggest you check the tank while being filled to determine which panels are flexing, and put wooden wedges or other suitable supports to stop the movement. If it is the bottom panel, several supports may be necessary.

I don't think you need to worry about this, your tank is not about to explode or anything nasty like that. You are also quite safe in continuing to enjoy the beans and cabbage. Brings new meaning to the expression "thunder pot". Incidentally, do you ever hear the same noise as you empty the tank?

Regarding your last question, I believe the word is HEAD, in the singular (unless you have two on board), and comes from the traditional location in old ships, at the bow, or head. There is a good nautical dictionary with historical explanations somewhere on the web, but darned if I can find it now. Maybe someone else knows where to look. Best regards

 

[bob_tyler]

Try this for a nautical dictionary.

http://www.boattalk.com/dictionary/

 

[steve]

British English--heads
American English--head