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cp5041 10-28-2006 08:39 PM

DIY wet/dry
I'm building my own wet/dry filter and I've had an one before but it kept overflowing my tank. I have a 55 gallon glass aquarium so I have to use an overflow. My question is how should I choose both the overflow box and the return pump without running the risk of overflowing the tank or sump. Or sucking the sump dry??????

trreherd 10-29-2006 07:59 PM

I think a single bulkhead will drain 600 gallons an hour so you should get a pump that does about that-I think if you pump is not pumping fast enuff and your sump is overflowing you can use a ball valve to slow the flow so the pump can keep up

porksnorkel 12-25-2006 05:44 PM

gotta have a ball valve on the intake side anyways in case u lose power or the pump seizes or something like that. 55g of water makes a very big mess.

fish_4_all 12-26-2006 01:43 AM

Agreed, best solution is a check valve for the sump, when it gets to apoint the valve can either slow or stop the flow and the pumps can catch up, it could also be rigged so that it increases flow when needed.

caferacermike 12-26-2006 07:04 AM

Y'all are not thinking correctly.

It doesn't matter what size the return pump is as long as it is not rated MORE than the overflow box. You do not need any checkvalves or ball valves.

I'm a pipe fitter, trust me on this one.

Run your overflow box wide open to the wet dry. You might want to run it in one size larger pipe, as in, if your bulkhead is 1" upsize your pipe to 1 1/4". It will run quieter. Typically you will run your return line about half your suction line. Where your return line bends back over the tank drill a small hole in the elbow just under the water line.

Now I want you to think about something. Your overflow box can ONLY work as fast as your return pump replaces the water. Period. Your water line in your tank will be dictated by the heigth of the overflow teeth. If your pump quits working it quits putting water back in the tank. You will only siphon about another 1/4" of tank water before the teeth are ABOVE the waterline. No magic happens here. One the teeth are above the waterline no more water can magically end up on the floor. It will not continue sucking 600g of water out of your tank. However, that hole you drilled in your return 90 will break suction just as soon as it is exposed to air. Generally as soon as the overflow box loses suction the return bend 90 also breaks suction. Of course this amount can vary due to placement of the hole. Drilling the hole will break any back siphon when it is exposed. Of course you may need to tinker with it a few times to adjust everything. Never just set it up and walk away, thinking it will work. Test it several times by unplugging the kit. Keep in mind that 99% of the overflow boxes will hold their suction in the tubing. So as soon as power is restored the pump will refill the tank to the appropriate heigth, at this point the cycle will begin anew. If for some reason after installing everythign you decide your return pump is to large you can add a ball valve on teh RETURN side to slow it down. Never add the valves to the suction side as it can cause a pump to run dry.

Let's review.

A properly set up overflow will only back siphon about a total of 1/2" of tank water from the display (for insurance purposes when I choose my sump I multiply my tanks lengthxwidth by whatever I need my sumps depth+2". The 2" is equuivalent to 2" of my tank draining back). Thereby your animals will not be in a dry tank. Your sump will increase about 4" in depth. If chosen wisely this is not a problem. If not chosen correctly (as in to small) you will end up with a few gallons on the floor. When the pump restarts it will fill the tank back up tothe overflow line and the cycle will restart.

porksnorkel 12-26-2006 11:26 AM

good post mike. now forgive my ignorance, but is it possible that not everyone has the overflow wall in their tank? just a pipe sucking from the bottom? this woulod of course drain the entire tank via gravity, in the event of pump failure. also i'm wondering what would happen if the seal on an overflow wall failed and is this common? would it be good insurance for someone who isn't confident in their set up to just add a check ball in the suction side?

another question...if u drill a hole in the pressure side of the system at the elbow, won't water be forced out of that hole and all over the nearest wall?

caferacermike 12-26-2006 07:59 PM

Drill the hole so it points down in the tank...Simple enough.

I don't know anyone silly enough to run a suction tube for a wetdry to the bottom of their tank. If so, bully for them, they get what they deserve. Anyone using only a utube for suction is just asking for problems, check valve or no. There is no one way to make them equal out. Just spend the $50 for an overflow box. BTW, I never once mentioned in my reply that this was advice for an internal overflow. My advice was for a HOT overflow. If for any reason someone was to attempt using only a Utube for suction then it should be cut no more than 1" below the surface and or at least have a hole drilled in it near the surface so that when exposed it breaks the siphon. However, when the pump kicks back on, NOTHING will restart the suction and your sump will overfill your tank causing serious damage to surrounding areas.

Your other question, if a seal should fail in a built in overflow. I've had this happen. Just like anything else, when enough water leaks out it cannot overflow the teeth, thereby ending the troubles. However your sump will dry and you could eat your pump.

Check valves are not adised by myself in your basic wet/dry set up. they fail. To many people would bet the farm on them and anything could cause it not to close properly. Also good luck finding one that would not be a serious restriction in the assembly. I install 12" backflows weekly. I'm pretty familar with check valves. If you could find a PVC swing check that is gravity fed you might have a decent product but I haven't seen any good ones. Spring checks are the only "sure fire" check valve.

A properly set up system needs only a 3/32 hole drilled just below the water line to break a back siphon.

fish_4_all 12-26-2006 08:32 PM

Makes sense to me, in words, but for those of us that are not "piping" inclined, :wink: , is there a diagram inline to look at this setup? It all sounds pretty simple and the safeties you explained are actually kinda cool. I always thought the intake tube was deep in the tank in order to remove the debris from the bottom and create circulation.

porksnorkel 12-26-2006 09:29 PM

i thought that too, fish...that the intake should be near the bottom of the tank to collect as much schmootz as possible. i had heard of drilling the intake at the top but i forgot to do that. unfortunately i just bit the bullet on that one. my cascade's seal failed and i have a lovely mess to contend w/ tommorrow. 3 tanks have to be drained and moved. i only lost a few gallons so it coulda been alot worse. i have just made my case for HOB's though. the cascade canister will find itself in the trash on thursday! now if u'll excuse me i have to go an order a new emperor HOB!

caferacermike 12-27-2006 07:45 PM

Canister filters are another thing. This was all about wet dry filters and sumps, not canisters. A canister filter should not be able to drain a tank. They are sealed units. But if you left it open.......Or removed it for cleaning but did not shut the valves for cleaning and just left the tubing dangling.........

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