Need some help with a constant drip system that isn't draining

[Massive Jim]

Hi Guys,

I have run a constant drop system now on my tank for a few years in my old property I just ran a bit of PVC pipe along the wall and drilled a hole in my front wall then put the very small diameter pipe into a small hole in a drainpipe outside.

I have recently moved house and had to change things around a bit, the location of my fish tank is the other side of a wall that has a toilet waste pipe from upstairs.
So I had a plumber drill a hole through the wall and attach a waste pipe strap boss to the waste for me which takes a washing machine waste pipe.

In the diagram below is a (very badly drawn) diagram of my setup.
I have a standpipe (1 1/4") inside my sump that is connected to an elbow that is connected to a bulkhead then another elbow facing up on the outside of the sump at the rear with another pipe that is slightly shorter than the one inside the sump, connected to that is a flexible pipe that runs through the wall at a lower point, then on the other side of the wall the waste pipe fits into the strap boss on the toilet waste pipe, which is lower still.

So overall the pipe does run downhill (more than enough to let water flow) but the problem is that the small dip in the flexible waste pipe on the fish tank side of the wall is preventing the sump from draining, if I fill up the sump it just doesn't drain, unless I go and jiggle the pipe which I think is creating a siphon temporarily, then it will drain properly, but as soon as the flexible pipe empties I am back to the same problem again.

I can't get my head around the problem, I guess there isn't enough water pressure to push the water back up hill where the pipe dips, I know the perfect solution is to cut the pipe shorter and pull it taught so that it has a constant fall with no dip in it, but in order to do that I would never be able to move my tank without pulling one of the pipes out of their fittings.

I didn't have this problem at the previous property because I didn't need the small "u bend" to trap gases from the waste pipe because i was tapped into a gutter downpipe outside.


Can anyone help ?

 

[fishdance]

Yes, the "valley"in your drain line is creating an air lock which needs water level pressure to build up before it can push through. This will create periodic siphons.

The safest solution is to remove the "valley" by lowering the wall penetration position. Or perhaps use a rigid drain line to eliminate the loop (valley). If using rigid drain, you can add a TEE and short riser as air vent. I fly screen these vents to prevent insects getting in.

You can use 2 different pipe diameters if you need to move sump/tank. So the inner pipe can slide in/ out of the outer one. However I'd just use a threaded screw bulkhead if your not moving the tank frequently.

 

[Massive Jim]

Yes, the "valley"in your drain line is creating an air lock which needs water level pressure to build up before it can push through. This will create periodic siphons.

The safest solution is to remove the "valley" by lowering the wall penetration position. Or perhaps use a rigid drain line to eliminate the loop (valley). If using rigid drain, you can add a TEE and short riser as air vent. I fly screen these vents to prevent insects getting in.

You can use 2 different pipe diameters if you need to move sump/tank. So the inner pipe can slide in/ out of the outer one. However I'd just use a threaded screw bulkhead if your not moving the tank frequently.

Thanks for the reply.
I can't add a t vent because of sewer gases escaping.
The wall penetration point is about as low as it can get without removing the fall on the other side of the wall.

Maybe I could replace a section of the flexi pipe with rigid, and have very short runs of flexi at each end.

 

[fishdance]

Put the flexible tube/valley on the outside if you need to trap vent gas. Creating your own trap. This will depend on how much fall is available outside.

Or add a separate dedicated P trap (on outside) to drop the waste water into.

Also - look into barrel union joints if you want to connect & disconnect pipe easily (when shifting tank). They are a screw together join. Multiple diameters available.

 

[fishdance]

How did you go with solving this?

If you don't want to adjust things much, another option is to place a breather TEE on the other side of "valley" just before the wall. The open end of TEE would need to be above tanks water level to release trapped air bubbles. This is not ideal as water will collect in the valley but once its filled, water will overflow out.

 

[Massive Jim]

It's draining OK at the minute without me doing anything.

The tank is a couple of feet away from the wall though, so when I move it back the dip in the pipe will be lower so I'm going to have to do something then.

 

[Krismo962]

wednesday13

 

[wednesday13]

wednesday13

Id redrill the drip drain hole/bulkhead in ur sump closer or at the water level… I dont think the light drip flow is enough to push that water through the bottom “u” shape and back up. Same as with a non drilled sump for drip water removal, the flow just isnt enough to keep a siphon through a u shaped overflow. Would drain “true” if u moved the bulkhead up with no restrictions of flow. I believe thats ur problem even before it gets to ur flex tubing on the outside.