I have a 3/4" True Union check valve on my return. When first installed it worked perfectly (about 3 months ago) now when i shut the pump off, the mechanism that is supposed to seal shut just knocks very loudly and vibrates the entire return line, basically it NEVER ends up sealing, it just keeps knocking. Has anyone had this issue? If someone is using a better 3/4" check valve, i'd love a link to it so i can change it out. I basically have the one from MD though i purchased it from Amazon. http://www.marinedepot.com/True_Uni...Valves-Plumbing_Parts-FT9133-FIFTVLTC-vi.html
Knocking Tru Union Swing Valve
- Thread starter jombolo
- Start date
RocketEngineer
Space is big.
something grew on the valve seat which is why check valves don't work in reef setups, the ecosystem we keep grows on every surface it can.
I hate to say it, but you are correct. I removed it and washed it out with hot water, works like a charm now.
What's your recommendation for a long term solution? I was looking at a ball type check valve that doesn't use this flap style, but wasn't cheap.
RocketEngineer
Space is big.
same problem. the solution is to not need a check valve. the sump should be large enough to accept all the drainage from the tank. thats why many of them run only half full so that when the return pump stops, there is plenty of volume left.
I'm 98% sure I have enough room in my sump to compensate if power is lost. I added the check valve as a paranoid redundancy. Surely a rocket engineer can understand paranoid redundancies
uncleof6
Active member
Well paranoid redundancy aside, 
, don't think you have enough room, KNOW you have enough room. If you don't have enough room, redesign the system so you do have enough room. The probability of failure for check valves, and anti-siphon holes is 100%. When designing a failsafe, redundancy is important, sure, but use a failsafe, the failure of which—makes the system safer, not a huge flood risk, or one that is passive. Class of failsafe="passive:" e.g. no moving parts, no electricity, no way to plug or clog, etc. Sump volume is the only passive failsafe for power out drain down.
, don't think you have enough room, KNOW you have enough room. If you don't have enough room, redesign the system so you do have enough room. The probability of failure for check valves, and anti-siphon holes is 100%. When designing a failsafe, redundancy is important, sure, but use a failsafe, the failure of which—makes the system safer, not a huge flood risk, or one that is passive. Class of failsafe="passive:" e.g. no moving parts, no electricity, no way to plug or clog, etc. Sump volume is the only passive failsafe for power out drain down.
woodnaquanut
Active member
What uncle said!
Test it. Turn off the return and skimmer, then watch what happens.
Test it. Turn off the return and skimmer, then watch what happens.
leveldrummer
New member
your return lines should be very close to water surface so when power is out, it only drains a little before it breaks syphon, Ive seen people run their returns 6-8" down into the tank, not knowing that they are about to syphon the top half of their tank dry incase of power outage.
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