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Mushroom vents


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8 minutes ago, jddevel said:

I know we`ve had some driving rain recently so is it common to find water has entered via the mushroom vents . Or is it due to the type of vents the hull manufacturers fitted please. They are the "mushroom" type.

How tall is the Upstand(fixed bit),my current ones have a 45 mm Up stand and don't allow Rain to bounce up to the inside of the top and drip into the Boat

The shallower versions(25-35 mm )do leak when Rain is heavy

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2 hours ago, jddevel said:

I know we`ve had some driving rain recently so is it common to find water has entered via the mushroom vents . Or is it due to the type of vents the hull manufacturers fitted please. They are the "mushroom" type.

Yes it happens periodically in very heavy downpours.

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Considering the design of mushroom vents is supposed to stop surface water getting in I would say no it is not common but we can only speak from our own experience. I've only ever had water getting past them when the seal has failed.  Quite a few people do seem to suffer from condensation in these vents (usually when there's a vent over the bed..) which can confuse the issue.   

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1 hour ago, Jen-in-Wellies said:

Hail stones bounce up from the roof and drop through mushroom vents very easily!

Jen

Nope, that's never happened to me, our vents are 100% watertight.

Maybe I've got, ahem, magic mushroom vents.

 

  • Greenie 1
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On a hot day, I unscrew them all the way, so that the rim is above the upstand; this allows warm air from the boat to escape.  When I'm cold, I screw them down and this helps trap warm air in the mushroom.  This also keeps the rain out.

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This is not unknown, and certainly while we find the issue very manageable, i would always advise a user fit them  over the corridor/bath or similar rather than over a bed or cupboard.

 - As said, some are better designed than others. Also be aware that some allow you to full close them, which causes issues for the BSS (now 'only' recommended) ventilation requirements unless you modify them by placing a nut or similar over the thread to limit travel.

 

Daniel

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4 hours ago, system 4-50 said:

I've got a leaky UFO. I thought that was impossible. I'll have to take it apart and see what is going on. It is on the centre line of the roof as well!

I've had leaky flying saucer vents I think it was something to do with the rubber gasket thingy.  As you say the design implies they can't leak but in my experience there's no orifice on a narrowboat that won't leak given time.  

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"On a hot day, I unscrew them all the way, so that the rim is above the upstand; this allows warm air from the boat to escape.  When I'm cold, I screw them down and this helps trap warm air in the mushroom.  This also keeps the rain out. "

Now that sounds like a business opportunity in some of the wealthier areas either a manually altered one carried out by marina staff or obliging other boat owners-for a small fee. Or perhaps design electrically operated ones. Mmm or perhaps thermostatically/humidity reactive. Could even operate via a smart phone. Oh I better stop I don`t know what I`m talking about and too much else to worry about.

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1 minute ago, jddevel said:

"On a hot day, I unscrew them all the way, so that the rim is above the upstand; this allows warm air from the boat to escape.  When I'm cold, I screw them down and this helps trap warm air in the mushroom.  This also keeps the rain out. "

Now that sounds like a business opportunity in some of the wealthier areas either a manually altered one carried out by marina staff or obliging other boat owners-for a small fee. Or perhaps design electrically operated ones. Mmm or perhaps thermostatically/humidity reactive. Could even operate via a smart phone. Oh I better stop I don`t know what I`m talking about and too much else to worry about.

Or just use the boat and turn the know with your hand.

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On 22/03/2017 at 13:39, cereal tiller said:

How tall is the Upstand(fixed bit),my current ones have a 45 mm Up stand and don't allow Rain to bounce up to the inside of the top and drip into the Boat

The shallower versions(25-35 mm )do leak when Rain is heavy

This very sensible response seems to have been ignored in almost every post that has followed it.

This is the key.

If the upstanding sides of the lower part are shallow, (say an inch or less), then very heavy rain will bounce off the roof hard enough that it the gets up under the covering dome, and can fall down inside that upstand.

This can happen even of the dome is screwed down so its bottom edge is lower than the top of the upstand, (although screwing it right down should limit the possibility considerably).

A quality vent will not skimp on metal, and will have maybe 2" of upstand above the base.  That is usually enough that even a very heavy downpour will not be hitting the roof hard enough for drops to bounce up high enough to get over the top edge.  Many of the vents sold are not quality.

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11 hours ago, alan_fincher said:

This very sensible response seems to have been ignored in almost every post that has followed it.

This is the key.

If the upstanding sides of the lower part are shallow, (say an inch or less), then very heavy rain will bounce off the roof hard enough that it the gets up under the covering dome, and can fall down inside that upstand.

This can happen even of the dome is screwed down so its bottom edge is lower than the top of the upstand, (although screwing it right down should limit the possibility considerably).

A quality vent will not skimp on metal, and will have maybe 2" of upstand above the base.  That is usually enough that even a very heavy downpour will not be hitting the roof hard enough for drops to bounce up high enough to get over the top edge.  Many of the vents sold are not quality.

My vents have a shallow upstand, about 30mil and I repeat I have never had a drop of rain/hail/snow through any of them.  The kitchen vent is actually set so you can't screw the cap down lower than the top edge of the upstand.  The fact that most of the time these vents are full of cobwebs confirms their dry status. 

What I do notice, and I haven't bothered to compare them with my neighbours boats, is the upstands on my vents are not vertical, they are slightly conical so I wonder if it's this feature that prevents the ingress of heavy rain. 

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