So I'm doing some water tank work and I've confirmed what I already suspected. My tanks are cross vented to one another through a low point loop. It appears that I could in theory fill all my tanks from one deck fill port despite having a fill port for each of my tanks. I'm thinking that tracking tank level is a challenge when they are all sluicing between one another. This doesn't seem advantageous. Why would the manufacturer do this. Is there a problem with me undoing it? Josh Muckley S/V Sea Hawk 1989 C&C 37+ Solomons, MD

On my LF38, all three tanks have their own individual vent as they should. The vent line follows the inlet hose and exits the hull just below each fill connection on the deck. The original vent lines are 3/8" gray plastic piping. A good venting system is necessary to get good flow into and out of the tank as well as insuring that the water pump does not pull a vacuum on the tank and cause it to implode--I have seen this happen on poorly vented holding tanks when emptied. Bob LF38 "Rainy Days" On Sep 8, 2015, at 2:55 PM, Josh Muckley via CnC-List wrote: > So I'm doing some water tank work and I've confirmed what I already suspected. My tanks are cross vented to one another through a low point loop. It appears that I could in theory fill all my tanks from one deck fill port despite having a fill port for each of my tanks. I'm thinking that tracking tank level is a challenge when they are all sluicing between one another. > > This doesn't seem advantageous. Why would the manufacturer do this. Is there a problem with me undoing it? > > Josh Muckley > S/V Sea Hawk > 1989 C&C 37+ > Solomons, MD > > _______________________________________________ > > Email address: > CnC-List@cnc-list.com > To change your list preferences, including unsubscribing -- go to the bottom of page at: > http://cnc-list.com/mailman/listinfo/cnc-list_cnc-list.com > Bob Boyer S/V Rainy Days (1983 C&C Landfall 38 - Hull #230) email: dainyrays@icloud.com blog: dainyrays.blogspot.com "There is nothing--absolutely nothing--half so much worth doing as simply messing about in boats." --Kenneth Grahame

As far as I can see, the only problem with not cross connecting the water tanks would be the resulting complexity of your fresh water system and the need to get access to all the valves every time you want to change tanks. You will need a line from each tank to the inlet of your fresh water pressure pump, and to each of the foot pumps on your boat. In addition, you would want to put a selector valve on the inlet of each pump – though I suppose you could use the water shutoff valve at the outlet of each tank to shut off the tank and isolate it from the rest of the water system. If you don’t put in some sort of valve to stop flow from the tank you do not intend to use to the pump, your tanks will still be cross connected; water will flow from the tank which is more full to the tank with the lower water level at through the connection just before the pump inlet. My 38 has 2 40 gallon tanks – one under each settee. There is a separate fill and vent for each. There is a shutoff valve in the outlet for each. Then water flows through a ½” hose to a “T” fitting under the cabin sole. The other two ½” hoses go forward and back to the sinks. The hose to the sink in the head forward goes to a foot pump. The line to the galley sink is the supply to the fresh water pressure pump, and also to the foot pump. The cross connection is down in the bilge, so even when heeled with mostly empty tanks the water in the tanks is above the suction line to the pump. If you are using only one tank, that tank is mostly empty, and the boat is heeled to that side, there is at least the possibility that there would not be water flow to the inlet of the water pump. Drawing water from the low side of the boat is not necessarily a bad thing. As far as filling all tanks from a single deck fill, the would be true in theory. But the cross connect through a ½” hose like mine would take a long time. The water into the deck fill through the garden hose would be a heck of a lot more than the gravity fed ½” connection could carry. All that said, there are times when you might want to keep one tank dry. I have 5 heavy batteries and a fair bit of added cabinetwork on the port side of my boat. Hence the boat rests with about a 2 degree list to port. I hit upon the idea of not using the port water tank the last time the tanks ran down, and shut off the valve on the outlet of the tank. That way the weight of the water in the starboard tank will offset some of the weight of the stuff to port, which took care of most of the list, and having only 40 gaallons of water is not much of a problem when not cruising. Rick Brass Washington, NC From: CnC-List [mailto:cnc-list-bounces@cnc-list.com] On Behalf Of Josh Muckley via CnC-List Sent: Tuesday, September 08, 2015 2:55 PM To: C&C List <cnc-list@cnc-list.com> Cc: Josh Muckley <muckleyj@gmail.com> Subject: Stus-List Water tank x-connect So I'm doing some water tank work and I've confirmed what I already suspected. My tanks are cross vented to one another through a low point loop. It appears that I could in theory fill all my tanks from one deck fill port despite having a fill port for each of my tanks. I'm thinking that tracking tank level is a challenge when they are all sluicing between one another. This doesn't seem advantageous. Why would the manufacturer do this. Is there a problem with me undoing it? Josh Muckley S/V Sea Hawk 1989 C&C 37+ Solomons, MD

Rick, Thanks for the response. I guess I'm not communicating my setup very well. I have a standard deck fill dedicated for each tank. Each tank also has a vent which exits the hull of the boat below the respective deck fill. I also have an outlet which goes to a 4 valve manifold and then to the suction side of the fresh water pump. This way I can select which tank to use (take suction from). All of this seems pretty normal and makes plenty of sense. The last part is where the confusion begins. Each tank has a fitting near the top and a pipe that is the same size as the vent and outlet. All of the tanks are connected solely to one another via this fitting and pipe. Since the pipe is routed down and under it creates a u-bend or trap between the tanks. If the water level in a tank is less than the height of this cross connect fitting then water is not cross connected. If, on the other hand the tank is full then it will "overflow" through the cross connect u-bend to one of the other tanks. Josh On Sep 9, 2015 11:01 AM, "Rick Brass via CnC-List" <cnc-list@cnc-list.com> wrote: > As far as I can see, the only problem with not cross connecting the water > tanks would be the resulting complexity of your fresh water system and the > need to get access to all the valves every time you want to change tanks. > > > > You will need a line from each tank to the inlet of your fresh water > pressure pump, and to each of the foot pumps on your boat. In addition, you > would want to put a selector valve on the inlet of each pump – though I > suppose you could use the water shutoff valve at the outlet of each tank to > shut off the tank and isolate it from the rest of the water system. If you > don’t put in some sort of valve to stop flow from the tank you do not > intend to use to the pump, your tanks will still be cross connected; water > will flow from the tank which is more full to the tank with the lower water > level at through the connection just before the pump inlet. > > > > My 38 has 2 40 gallon tanks – one under each settee. There is a separate > fill and vent for each. There is a shutoff valve in the outlet for each. > Then water flows through a ½” hose to a “T” fitting under the cabin sole. > The other two ½” hoses go forward and back to the sinks. The hose to the > sink in the head forward goes to a foot pump. The line to the galley sink > is the supply to the fresh water pressure pump, and also to the foot pump. > > > > The cross connection is down in the bilge, so even when heeled with mostly > empty tanks the water in the tanks is above the suction line to the pump. > If you are using only one tank, that tank is mostly empty, and the boat is > heeled to that side, there is at least the possibility that there would not > be water flow to the inlet of the water pump. Drawing water from the low > side of the boat is not necessarily a bad thing. > > > > As far as filling all tanks from a single deck fill, the would be true in > theory. But the cross connect through a ½” hose like mine would take a long > time. The water into the deck fill through the garden hose would be a heck > of a lot more than the gravity fed ½” connection could carry. > > > > All that said, there are times when you might want to keep one tank dry. I > have 5 heavy batteries and a fair bit of added cabinetwork on the port side > of my boat. Hence the boat rests with about a 2 degree list to port. I hit > upon the idea of not using the port water tank the last time the tanks ran > down, and shut off the valve on the outlet of the tank. That way the weight > of the water in the starboard tank will offset some of the weight of the > stuff to port, which took care of most of the list, and having only 40 > gaallons of water is not much of a problem when not cruising. > > > > > > Rick Brass > > Washington, NC > > > > > > > > *From:* CnC-List [mailto:cnc-list-bounces@cnc-list.com] *On Behalf Of *Josh > Muckley via CnC-List > *Sent:* Tuesday, September 08, 2015 2:55 PM > *To:* C&C List <cnc-list@cnc-list.com> > *Cc:* Josh Muckley <muckleyj@gmail.com> > *Subject:* Stus-List Water tank x-connect > > > > So I'm doing some water tank work and I've confirmed what I already > suspected. My tanks are cross vented to one another through a low point > loop. It appears that I could in theory fill all my tanks from one deck > fill port despite having a fill port for each of my tanks. I'm thinking > that tracking tank level is a challenge when they are all sluicing between > one another. > > This doesn't seem advantageous. Why would the manufacturer do this. Is > there a problem with me undoing it? > > Josh Muckley > S/V Sea Hawk > 1989 C&C 37+ > Solomons, MD > > _______________________________________________ > > Email address: > CnC-List@cnc-list.com > To change your list preferences, including unsubscribing -- go to the > bottom of page at: > http://cnc-list.com/mailman/listinfo/cnc-list_cnc-list.com > > >

So after some further investigation, all the tanks lead to a 4-way junction below the floor board access at the bottom of the companionway stairs. There are no valves or other separations between the three tanks. The 4th leg of the junction goes to a valve and then to one of the galley sink "faucets". I still don't get it. I guess the PO had a use for it all. Here I was thinking that there was a good engineering reason for tying the tanks together. It's gone now. Josh Muckley S/V Sea Hawk 1989 C&C 37+ Solomons, MD On Sep 9, 2015 12:14 PM, "Josh Muckley" <muckleyj@gmail.com> wrote: > Rick, > > Thanks for the response. I guess I'm not communicating my setup very > well. I have a standard deck fill dedicated for each tank. Each tank also > has a vent which exits the hull of the boat below the respective deck > fill. I also have an outlet which goes to a 4 valve manifold and then to > the suction side of the fresh water pump. This way I can select which tank > to use (take suction from). All of this seems pretty normal and makes > plenty of sense. The last part is where the confusion begins. Each tank > has a fitting near the top and a pipe that is the same size as the vent and > outlet. All of the tanks are connected solely to one another via this > fitting and pipe. Since the pipe is routed down and under it creates a > u-bend or trap between the tanks. If the water level in a tank is less > than the height of this cross connect fitting then water is not cross > connected. If, on the other hand the tank is full then it will "overflow" > through the cross connect u-bend to one of the other tanks. > > Josh > On Sep 9, 2015 11:01 AM, "Rick Brass via CnC-List" <cnc-list@cnc-list.com> > wrote: > >> As far as I can see, the only problem with not cross connecting the water >> tanks would be the resulting complexity of your fresh water system and the >> need to get access to all the valves every time you want to change tanks. >> >> >> >> You will need a line from each tank to the inlet of your fresh water >> pressure pump, and to each of the foot pumps on your boat. In addition, you >> would want to put a selector valve on the inlet of each pump – though I >> suppose you could use the water shutoff valve at the outlet of each tank to >> shut off the tank and isolate it from the rest of the water system. If you >> don’t put in some sort of valve to stop flow from the tank you do not >> intend to use to the pump, your tanks will still be cross connected; water >> will flow from the tank which is more full to the tank with the lower water >> level at through the connection just before the pump inlet. >> >> >> >> My 38 has 2 40 gallon tanks – one under each settee. There is a separate >> fill and vent for each. There is a shutoff valve in the outlet for each. >> Then water flows through a ½” hose to a “T” fitting under the cabin sole. >> The other two ½” hoses go forward and back to the sinks. The hose to the >> sink in the head forward goes to a foot pump. The line to the galley sink >> is the supply to the fresh water pressure pump, and also to the foot pump. >> >> >> >> The cross connection is down in the bilge, so even when heeled with >> mostly empty tanks the water in the tanks is above the suction line to the >> pump. If you are using only one tank, that tank is mostly empty, and the >> boat is heeled to that side, there is at least the possibility that there >> would not be water flow to the inlet of the water pump. Drawing water from >> the low side of the boat is not necessarily a bad thing. >> >> >> >> As far as filling all tanks from a single deck fill, the would be true in >> theory. But the cross connect through a ½” hose like mine would take a long >> time. The water into the deck fill through the garden hose would be a heck >> of a lot more than the gravity fed ½” connection could carry. >> >> >> >> All that said, there are times when you might want to keep one tank dry. >> I have 5 heavy batteries and a fair bit of added cabinetwork on the port >> side of my boat. Hence the boat rests with about a 2 degree list to port. I >> hit upon the idea of not using the port water tank the last time the tanks >> ran down, and shut off the valve on the outlet of the tank. That way the >> weight of the water in the starboard tank will offset some of the weight of >> the stuff to port, which took care of most of the list, and having only 40 >> gaallons of water is not much of a problem when not cruising. >> >> >> >> >> >> Rick Brass >> >> Washington, NC >> >> >> >> >> >> >> >> *From:* CnC-List [mailto:cnc-list-bounces@cnc-list.com] *On Behalf Of *Josh >> Muckley via CnC-List >> *Sent:* Tuesday, September 08, 2015 2:55 PM >> *To:* C&C List <cnc-list@cnc-list.com> >> *Cc:* Josh Muckley <muckleyj@gmail.com> >> *Subject:* Stus-List Water tank x-connect >> >> >> >> So I'm doing some water tank work and I've confirmed what I already >> suspected. My tanks are cross vented to one another through a low point >> loop. It appears that I could in theory fill all my tanks from one deck >> fill port despite having a fill port for each of my tanks. I'm thinking >> that tracking tank level is a challenge when they are all sluicing between >> one another. >> >> This doesn't seem advantageous. Why would the manufacturer do this. Is >> there a problem with me undoing it? >> >> Josh Muckley >> S/V Sea Hawk >> 1989 C&C 37+ >> Solomons, MD >> >> _______________________________________________ >> >> Email address: >> CnC-List@cnc-list.com >> To change your list preferences, including unsubscribing -- go to the >> bottom of page at: >> http://cnc-list.com/mailman/listinfo/cnc-list_cnc-list.com >> >> >>

Tying the tanks together wouldn't allow you to isolate one if you had a leak or something. Doesn't sound like a good idea to me. Bob Boyer S/V Rainy Days / Annapolis MD 1983 C&C Landfall 38 - Hull #230 email: dainyrays@iCloud.com blog: dainyrays.blogspot.com "There is nothing--absolutely nothing--half so much worth doing as simply messing about in boats." --Kenneth Grahame > On Sep 10, 2015, at 12:31 PM, Josh Muckley via CnC-List <cnc-list@cnc-list.com> wrote: > > So after some further investigation, all the tanks lead to a 4-way junction below the floor board access at the bottom of the companionway stairs. There are no valves or other separations between the three tanks. The 4th leg of the junction goes to a valve and then to one of the galley sink "faucets". > > I still don't get it. I guess the PO had a use for it all. Here I was thinking that there was a good engineering reason for tying the tanks together. > > It's gone now. > > Josh Muckley > S/V Sea Hawk > 1989 C&C 37+ > Solomons, MD > >> On Sep 9, 2015 12:14 PM, "Josh Muckley" <muckleyj@gmail.com> wrote: >> Rick, >> >> Thanks for the response. I guess I'm not communicating my setup very well. I have a standard deck fill dedicated for each tank. Each tank also has a vent which exits the hull of the boat below the respective deck fill. I also have an outlet which goes to a 4 valve manifold and then to the suction side of the fresh water pump. This way I can select which tank to use (take suction from). All of this seems pretty normal and makes plenty of sense. The last part is where the confusion begins. Each tank has a fitting near the top and a pipe that is the same size as the vent and outlet. All of the tanks are connected solely to one another via this fitting and pipe. Since the pipe is routed down and under it creates a u-bend or trap between the tanks. If the water level in a tank is less than the height of this cross connect fitting then water is not cross connected. If, on the other hand the tank is full then it will "overflow" through the cross connect u-bend to one of the other tanks. >> >> Josh >> >>> On Sep 9, 2015 11:01 AM, "Rick Brass via CnC-List" <cnc-list@cnc-list.com> wrote: >>> As far as I can see, the only problem with not cross connecting the water tanks would be the resulting complexity of your fresh water system and the need to get access to all the valves every time you want to change tanks. >>> >>> >>> >>> You will need a line from each tank to the inlet of your fresh water pressure pump, and to each of the foot pumps on your boat. In addition, you would want to put a selector valve on the inlet of each pump – though I suppose you could use the water shutoff valve at the outlet of each tank to shut off the tank and isolate it from the rest of the water system. If you don’t put in some sort of valve to stop flow from the tank you do not intend to use to the pump, your tanks will still be cross connected; water will flow from the tank which is more full to the tank with the lower water level at through the connection just before the pump inlet. >>> >>> >>> >>> My 38 has 2 40 gallon tanks – one under each settee. There is a separate fill and vent for each. There is a shutoff valve in the outlet for each. Then water flows through a ½” hose to a “T” fitting under the cabin sole. The other two ½” hoses go forward and back to the sinks. The hose to the sink in the head forward goes to a foot pump. The line to the galley sink is the supply to the fresh water pressure pump, and also to the foot pump. >>> >>> >>> >>> The cross connection is down in the bilge, so even when heeled with mostly empty tanks the water in the tanks is above the suction line to the pump. If you are using only one tank, that tank is mostly empty, and the boat is heeled to that side, there is at least the possibility that there would not be water flow to the inlet of the water pump. Drawing water from the low side of the boat is not necessarily a bad thing. >>> >>> >>> >>> As far as filling all tanks from a single deck fill, the would be true in theory. But the cross connect through a ½” hose like mine would take a long time. The water into the deck fill through the garden hose would be a heck of a lot more than the gravity fed ½” connection could carry. >>> >>> >>> >>> All that said, there are times when you might want to keep one tank dry. I have 5 heavy batteries and a fair bit of added cabinetwork on the port side of my boat. Hence the boat rests with about a 2 degree list to port. I hit upon the idea of not using the port water tank the last time the tanks ran down, and shut off the valve on the outlet of the tank. That way the weight of the water in the starboard tank will offset some of the weight of the stuff to port, which took care of most of the list, and having only 40 gaallons of water is not much of a problem when not cruising. >>> >>> >>> >>> >>> >>> Rick Brass >>> >>> Washington, NC >>> >>> >>> >>> >>> >>> >>> >>> From: CnC-List [mailto:cnc-list-bounces@cnc-list.com] On Behalf Of Josh Muckley via CnC-List >>> Sent: Tuesday, September 08, 2015 2:55 PM >>> To: C&C List <cnc-list@cnc-list.com> >>> Cc: Josh Muckley <muckleyj@gmail.com> >>> Subject: Stus-List Water tank x-connect >>> >>> >>> >>> So I'm doing some water tank work and I've confirmed what I already suspected. My tanks are cross vented to one another through a low point loop. It appears that I could in theory fill all my tanks from one deck fill port despite having a fill port for each of my tanks. I'm thinking that tracking tank level is a challenge when they are all sluicing between one another. >>> >>> This doesn't seem advantageous. Why would the manufacturer do this. Is there a problem with me undoing it? >>> >>> Josh Muckley >>> S/V Sea Hawk >>> 1989 C&C 37+ >>> Solomons, MD >>> >>> >>> _______________________________________________ >>> >>> Email address: >>> CnC-List@cnc-list.com >>> To change your list preferences, including unsubscribing -- go to the bottom of page at: >>> http://cnc-list.com/mailman/listinfo/cnc-list_cnc-list.com >>> >>> > _______________________________________________ > > Email address: > CnC-List@cnc-list.com > To change your list preferences, including unsubscribing -- go to the bottom of page at: > http://cnc-list.com/mailman/listinfo/cnc-list_cnc-list.com >