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Pressure
Peggy, You are right in some of your assumptions, reduction of pressure when the system is opened, and definitely right about the need for pressure reduction to protect a weaker system from a stronger system (such as shore to boat systems). Where you went wrong was the assumption that going from a large pipe to a smaller pipe (the hose you first mentioned) would increase pressure and therefore cause the need for a pressure reducer. The problem is in the assumptions. If you assume that a small pipe will carry the same volume of water as a larger pipe, then the small pipe has to be at higher pressure. Think of it as two pipes in seperate systems, where you want the same rate of flow out the end of each pipe to be equal. The problem is, that does not exist in a water system. The maximum pressure of a water system at any instant is whatever exists in the static situation. In a water system, a smaller pipe just simply carries less volume, at the same pressure as the larger pipe. That's why the water lines in the street are large, and the connections to the houses are small. It's a matter of volume, at equal pressure. If, as you were thinking, pressure increased in proportion to the reduction in pipe size, the water lines could be the same size in the street as at the house. So we disagree that a smaller pipe in the same system will be at a higher pressure, it will not. Now we could get complicated and talk about pressure getting lower as you near the open end of the system. Or, the possibility of sudden shut-off causing overpressure situations. But, basically, it does not matter where you put a pressure gauge on a closed water system the 10" pipe in the street or the 1/2" faucet at the dock, the pressure will be substantially the same, as long as reasonable proximity exists and no intervening pressure reducers or mechanical pumps exist. Hope this helps. And, thank you for all the things I've learned about my boat from you. Dan Jonas (S/V Feije II)
Peggy, You are right in some of your assumptions, reduction of pressure when the system is opened, and definitely right about the need for pressure reduction to protect a weaker system from a stronger system (such as shore to boat systems). Where you went wrong was the assumption that going from a large pipe to a smaller pipe (the hose you first mentioned) would increase pressure and therefore cause the need for a pressure reducer. The problem is in the assumptions. If you assume that a small pipe will carry the same volume of water as a larger pipe, then the small pipe has to be at higher pressure. Think of it as two pipes in seperate systems, where you want the same rate of flow out the end of each pipe to be equal. The problem is, that does not exist in a water system. The maximum pressure of a water system at any instant is whatever exists in the static situation. In a water system, a smaller pipe just simply carries less volume, at the same pressure as the larger pipe. That's why the water lines in the street are large, and the connections to the houses are small. It's a matter of volume, at equal pressure. If, as you were thinking, pressure increased in proportion to the reduction in pipe size, the water lines could be the same size in the street as at the house. So we disagree that a smaller pipe in the same system will be at a higher pressure, it will not. Now we could get complicated and talk about pressure getting lower as you near the open end of the system. Or, the possibility of sudden shut-off causing overpressure situations. But, basically, it does not matter where you put a pressure gauge on a closed water system the 10" pipe in the street or the 1/2" faucet at the dock, the pressure will be substantially the same, as long as reasonable proximity exists and no intervening pressure reducers or mechanical pumps exist. Hope this helps. And, thank you for all the things I've learned about my boat from you. Dan Jonas (S/V Feije II)
Hmmmm...
I THINK I get it, now...but I still have questions. I won't belabor it here on the board any longer, though.. It would be SO much easier if we were discussing it over a couple of beers with a pen and about 2 dozen bar napkins.
Thanks, Dan.
I THINK I get it, now...but I still have questions. I won't belabor it here on the board any longer, though.. It would be SO much easier if we were discussing it over a couple of beers with a pen and about 2 dozen bar napkins.
Thanks, Dan.Meeting for a beer
That would be fun Peggy, but I think splitting the difference, it would be a bar somewhere around Colorado? My email is dan.jonas@starband.net if you desire. Dan Jonas (S/V Feije II)
That would be fun Peggy, but I think splitting the difference, it would be a bar somewhere around Colorado? My email is dan.jonas@starband.net if you desire. Dan Jonas (S/V Feije II)
Beer Pressure
In considering my ideal dockside pressure water system that I detailed below, I did open a hole in a pressure vessle and proceded to to introduce the contents into a larger vessle. Pressure was lowered in all vessles. My thanks to everyone who has contributed to make this one of the more interesting topics on the forum! PS: Never drink beer through a straw!
In considering my ideal dockside pressure water system that I detailed below, I did open a hole in a pressure vessle and proceded to to introduce the contents into a larger vessle. Pressure was lowered in all vessles. My thanks to everyone who has contributed to make this one of the more interesting topics on the forum! PS: Never drink beer through a straw!
Actually, pressure should have INCREASED
in the final vessel into which the beer went...which, fortunately, nature equipped with a "pressure relief valve."
in the final vessel into which the beer went...which, fortunately, nature equipped with a "pressure relief valve."
Btw, Dan...
I think you 'left coast' Hunter Owners should organize a Hunter Rendevous of the same kind the Chesepeake Bay gang has every two years. They invite speakers on all kinds of topics, from cruising destinations to provisioning to rigging, wiring, and plumbing...draw over 200 people--about half by boat and about half by land--and combine it with a regatta, a really squirrely dinghy race (blindfolded), drinkin' and dancin' and games. It's 3 days of the most fun you can have with your clothes on!
I think you 'left coast' Hunter Owners should organize a Hunter Rendevous of the same kind the Chesepeake Bay gang has every two years. They invite speakers on all kinds of topics, from cruising destinations to provisioning to rigging, wiring, and plumbing...draw over 200 people--about half by boat and about half by land--and combine it with a regatta, a really squirrely dinghy race (blindfolded), drinkin' and dancin' and games. It's 3 days of the most fun you can have with your clothes on!
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