Stopping back syphon on a rack system

[jim barry]

I have a problem on a rack system (this is a different system/different question to my post regards where to drill anti syphon holes)
I have a rack system with 3 display tanks and one sump. Problem is that if the power goes I have too much water leaving each display tank. The sump I have plumbed to waste for auto drip and I can't increase the water height in the sump to allow the amount of water that leaves each display tank in the event of the return pump stopping. Ideally the sump needs to be taller so it can hold more volume but the sump is the sump and is as big as can be. If I make the sump baffles taller so it can hold more water the baffles will become ineffective as the water will not circulate across the media as it should.
You could say I am a little baffled!
I have had this rack system for a couple of years and have already increased the height of the baffles as high as I can to increase the volume of water as much as I can, but its still not enough. So when the power goes, the water leaves each display tank, enters the sump and then drains out the drain used for the auto drip drain. Then when the return pump is switched back on the water leaves the sump and re-fills the display tanks but then there is too little water left in the sump and I have to manually top it up.
All this is easily dealt with so long as I am at home. But if it were a power cut and I am not home, if the power comes back on I run the risk of the return pump running dry.
Any ideas people?

 

[Fguinan]

It sounds like the baffles in the sump are too high! If they are lower than amount of water in the sump will be less when the pump is running but will allow the water from the display tanks to drain into the sump when the pump is off without reaching the overflow level.

 

[BIG-G]

I have a problem on a rack system (this is a different system/different question to my post regards where to drill anti syphon holes)
I have a rack system with 3 display tanks and one sump. Problem is that if the power goes I have too much water leaving each display tank. The sump I have plumbed to waste for auto drip and I can't increase the water height in the sump to allow the amount of water that leaves each display tank in the event of the return pump stopping. Ideally the sump needs to be taller so it can hold more volume but the sump is the sump and is as big as can be. If I make the sump baffles taller so it can hold more water the baffles will become ineffective as the water will not circulate across the media as it should.
You could say I am a little baffled!
I have had this rack system for a couple of years and have already increased the height of the baffles as high as I can to increase the volume of water as much as I can, but its still not enough. So when the power goes, the water leaves each display tank, enters the sump and then drains out the drain used for the auto drip drain. Then when the return pump is switched back on the water leaves the sump and re-fills the display tanks but then there is too little water left in the sump and I have to manually top it up.
All this is easily dealt with so long as I am at home. But if it were a power cut and I am not home, if the power comes back on I run the risk of the return pump running dry.
Any ideas people?

Is there any room in the display tanks to set the level of the plumbing higher to stop as much water draining back to the sump?
Could be something as simple as adding an elbow that can be turned to adjust the water hight
I have a tank with a sump system that I wanted the drain to be deep near the bottom. So I drill a small hole at the top of the elbow going to the sump as a siphon break. Is that something that could work?

 

[esoxlucius]

The ideal solution which gives you 99% peace of mind is to get a bigger sump to service that expected overflow of water from those three tanks. But you already know this. Am i right in thinking that a bigger sump, for whatever reason, is a complete non starter, because personally i'd be jumping through hoops to make that option work, somehow.

If it is a non starter then to be honest I think this problem can be improved upon by looking no further than your other thread regarding the syphon holes. You are always going to get some back syphon, just from the pipework for a start, but to ensure that as little tank water back syphons as possible then it is critical that your syphon is stopped very quickly, more or less as soon as the pump goes off.

Drilling your syphon holes above water level will ensure the syphon is stopped as fast as it can be, as mentioned in your other thread. This would REDUCE the overspill from those three tanks, but NOT stop it altogether. The true test is to see if your sump can take even this reduced overspill and not reach your auto top up drain.

Some people might suggest check valves on the vertical part of your return line. Pump goes off, check valve stops water flow back to sump. However, most hobbyists consider check valves accidents waiting to happen.

TheWolfman , twentyleagues , ragin_cajun .

 

[fishdance]

I solved a similar situation on a system that has constant drip input. I placed an auto start siphon to drain on the sump. So when power fails, water drops, sump fills then siphon drain starts up. A siphon can pull water much faster than a gravity fed drain.

When sump level drops the siphon stops. When power is returned the water pump restarts, sump level is very low but it self fills over time.

Any size rack and sump is suitable. On this one I have 20 x 500L tanks on a tiny 200L shallow sump.

Send me a PM if you want photos. I don't share images publicly.

 

[TheWolfman]

The issue is a combination of the drip and the size of the return chamber. You’ll always have waste water on power failure with the overflow inside the sump. A larger return chamber, or removing the baffles in the sump all together would provide the extra reserve the return pump needs until the drip catches back up. Limiting the amount of water that drains down to the sump will help. Stand pipes at the proper height inside your overflows will help reduce the amount of water draining. A check valve above the return pump will help and should only be used as extra insurance and should not to be fully relied on . The stand pipe inside sump being set at the appropriate height will be a balancing act between return pump capacity and flooding on power loss. All these items will need to be dialed in order to run the drip. A larger sump would be the easiest fix.

 

[jim barry]

It sounds like the baffles in the sump are too high! If they are lower than amount of water in the sump will be less when the pump is running but will allow the water from the display tanks to drain into the sump when the pump is off without reaching the overflow level.

No, the water level in sump is set to the height of the overflow for the auto water changer, so when power out to pump the drained water just disasters down the drain.

 

[jim barry]

The ideal solution which gives you 99% peace of mind is to get a bigger sump to service that expected overflow of water from those three tanks. But you already know this. Am i right in thinking that a bigger sump, for whatever reason, is a complete non starter, because personally i'd be jumping through hoops to make that option work, somehow.

If it is a non starter then to be honest I think this problem can be improved upon by looking no further than your other thread regarding the syphon holes. You are always going to get some back syphon, just from the pipework for a start, but to ensure that as little tank water back syphons as possible then it is critical that your syphon is stopped very quickly, more or less as soon as the pump goes off.

Drilling your syphon holes above water level will ensure the syphon is stopped as fast as it can be, as mentioned in your other thread. This would REDUCE the overspill from those three tanks, but NOT stop it altogether. The true test is to see if your sump can take even this reduced overspill and not reach your auto top up drain.

Some people might suggest check valves on the vertical part of your return line. Pump goes off, check valve stops water flow back to sump. However, most hobbyists consider check valves accidents waiting to happen.

TheWolfman , twentyleagues , ragin_cajun .

Unfortunately I cant get to the back of the rack and plumbing without draining all tanks as its set against the wall. The drain and returns in each tank are a little weird, I will post some pics later. I wonder if some airline put down each drain will do the trick?

 

[jim barry]

The issue is a combination of the drip and the size of the return chamber. You’ll always have waste water on power failure with the overflow inside the sump. A larger return chamber, or removing the baffles in the sump all together would provide the extra reserve the return pump needs until the drip catches back up. Limiting the amount of water that drains down to the sump will help. Stand pipes at the proper height inside your overflows will help reduce the amount of water draining. A check valve above the return pump will help and should only be used as extra insurance and should not to be fully relied on . The stand pipe inside sump being set at the appropriate height will be a balancing act between return pump capacity and flooding on power loss. All these items will need to be dialed in order to run the drip. A larger sump would be the easiest fix.

No stand pipes or anything like that in this rack system. I bought it second hand and it comes with it's flaws. I will post some pics later so we understand better. But thanks for the valued input mate, appreciate it, and yes a larger sump would be the way forward but not possible.

 

[fishdance]

Maybe you can link a second sump by pipes, have done that but not ideal and pipe diameter needs to be a lot bigger than you expect.

Check valves are a disaster waiting to happen.