Pressure Relief Valves

Does anyone use a pressure relief valve on their ballast system? I was wandering if you could find one to install as a full indicator. My system uses PVC pipe going to the sacs, but I only have one tube to each that is for filling and draining. I split it near the front of the run to go to the drain. What I was thinking about is adding a vent line to the system with a pressure relief valve that would release with a low pressure when the sacks are about full. Then I could know without looking that they are full and shut off the pumps. Any thoughts?

Check out the check valves that Cliff used on his system. Post titled Ballast System Completed. He included a picture of the 1/2 and 3/4 version with part numbers.

I saw that he used the whale valves. Do they release at certain pressure? My thinking here is that if they release with no pressure, then they would allow water to flow out of them as soon as you turn on the pumps. Does that make sense? I am thinking something with a little bit of resistance that would not let water flow until the pressure increased with full sacs. Then would seal again when the pressure dropped after the pumps were shut off.

the ones I was looking at were made by legend and you could get them in differnt weight resistence. I was looking at the .5 pound.

Chris,

I didn't want any restriction on my burping lines. My theory being that you want to purge all the air out while filling to prevent unnecessary pressure on the sacks, and to insure that they are filled to there maximum capacity. I'm curious as to why you would want to build pressure in your sacks other than the water when filled???

Cliff,
I am using waterbed tubes and a twin waterbed mattress for my sacs, so they only have one valve on them. This means that I use the same line to fill and drain. I have a T fitting on it that goes to the fill and drain pumps to seperate the systems. In my setup, I could run a vent line off the main line to vent when the bags are full, but it would vent the entire time it is filling, therefore I need a pressure relief valve to allow the bags to fill first before the vent line opens up. I know it may be hard to follow, and I don't have the drawing of my system right now. I wil do another drawing and post it for you guys to see what i am talking about.

Not sure if this will work since I saved it as a word doc.

ballast Doc2.doc (21.5 k)

Ok, you can click on it and see my current set up. Actually, since I already have a Rule 1100 GPH aerator type pumps, would that cause enough resistance to the line to allow filing first before it blows through the pump?

OK, I understand now.

I as actually going to use the check valve when I was originally going to tap into the bilge line for draining. I did not want my sac draining into the bilge by mistake.