HOB Overflow Emergency Side Drain?

[Drew1600]

Hi all,

I purchased an Eshopps PF-300 Overflow (single drain) and was wondering if I should drill a hole in the side of the box, near the top, to act as a secondary emergency drain? Thank you so much for the input, it is greatly appreciated.

 

[MnFish1]

Hi all,

I purchased an Eshopps PF-300 Overflow (single drain) and was wondering if I should drill a hole in the side of the box, near the top, to act as a secondary emergency drain? Thank you so much for the input, it is greatly appreciated.

For what purpose? Where would the water drain? Without a picture its a little unclear what you're asking?

 

[Drew1600]

A single drain runs out of the bottom of the box. If this drain were to ever be plugged/compromised the overflow would stop, pump would continue, and DT would overflow. Though I am adding a float switch to combat this. So, by drilling a second hole on the side of the box, near the top, and running a second drain line an emergency drain would be created in the event of drain 1 clogging. Hole would be drilled above the regular water line, so it would only be used in the event of an overflow.

 

[Joe31415]

I'd be really nervous drilling a hole that big in a hundred dollar piece of acrylic. You could certainly try it and plan on buying an overflow with 2 (or 3) holes instead of one if it shatters. But I'm thinking you're better off making sure you use that little foam filter and clean it very regularly. Not just when you notice a slow down, but like every few days. Or even better, get rid of the filter altogether and put a standpipe in there so it's less likely to get clogged in the first place.

 

[Drew1600]

Standpipe will be my first mod I think I'll pass on drilling and rely on the float switch for now. Thank you!

 

[Dkmoo]

How big is sump's return chamber and do you have an ATO? If so, dimension?

Also how big is the tank?

Keep in mind that the OF box leaves aboutb2 inches of room in your tank, if its plugged, water will pump into the DT but it will not be unlimited. It will only pump to the max volume of the return chamber. Oftentimes a sump's return chamber for a sump of a "compatible size to DT will have an return chamber volume smaller than the remaining volume from the DT as a redundancy failsafe to prevent flooding.

 

[Joe31415]

How big is sump's return chamber and do you have an ATO? If so, dimension?

Also how big is the tank?

Keep in mind that the OF box leaves aboutb2 inches of room in your tank, if its plugged, water will pump into the DT but it will not be unlimited. It will only pump to the max volume of the return chamber. Oftentimes a sump's return chamber for a sump of a "compatible size to DT will have an return chamber volume smaller than the remaining volume from the DT as a redundancy failsafe to prevent flooding.

Except your overflow box isn't necessarily level with (or higher than) the rim of the tank. On my tank, for example, my overflow box sits below the rim of the tank. If I shut off the drain (and plug the emergency drain), water will get pumped into the DT, flow out to the overflow box and then pour over the side of it. Don't get me wrong, I still have a little bit of time and it'll still hold some of the extra water but the extra capacity that my DT can hold is the difference between the (current) water level and the top of the overflow box, not the top of the tank.

It should be noted, however, that I have a rimmed (and drilled) tank so my overflow box can't make it all the way to the top. If you have a rimless tank, YMMV and I haven't given any thought to what happens when you have an over the top/siphon type overflow box.

Something that would be interesting, but no doubt come with it's own set of problems would be a bulkhead (or over the top siphon) with a valve in it that would shut off flow to the overflow box when it notices the water stopped draining. That would allow the tank to fill all the way up to the rim and buy you the extra volume.

 

[Dkmoo]

Except your overflow box isn't necessarily level with (or higher than) the rim of the tank. On my tank, for example, my overflow box sits below the rim of the tank. If I shut off the drain (and plug the emergency drain), water will get pumped into the DT, flow out to the overflow box and then pour over the side of it. Don't get me wrong, I still have a little bit of time and it'll still hold some of the extra water but the extra capacity that my DT can hold is the difference between the (current) water level and the top of the overflow box, not the top of the tank.

It should be noted, however, that I have a rimmed (and drilled) tank so my overflow box can't make it all the way to the top. If you have a rimless tank, YMMV and I haven't given any thought to what happens when you have an over the top/siphon type overflow box.

Something that would be interesting, but no doubt come with it's own set of problems would be a bulkhead (or over the top siphon) with a valve in it that would shut off flow to the overflow box when it notices the water stopped draining. That would allow the tank to fill all the way up to the rim and buy you the extra volume.

Fair point. My tank actually had a clogged OF one time where pump rate exceeded drain rate. And I came home to a tank filled to the rim, and empty return chamber, and return pump spewing put air, but no flood. I did set my waterline a bit low from how I set up the HOB overflow.

Back to OPs question tho, I think my point is still something he should consider to see if its even possible to overflow with his tank dimension and water level, before risking drilling holes in something.