Minimum Clearances when drilling an overflow

[ensquire]

My overflow has 2 holes right now and I'm gonna do a Herbie, but space is tight. It currently has a main drain thru a 1" bulkead and a 1/2 bulkhead for the emergency overflow. I tested it running a Quiet one 4000 for the return at about 4' of rise to the head. ran return wide open and had to throttle down drain to maintain siphon. stopped main drain and it wasn't a big enough emergency line.
My options are a 3/4" or a 1' bulkhead . 3/4 might handle it but would be even safer at 1'.
Which bring me to this question. If I drill a 1 3/4" hole in the space available for the 1" bulkead there will only be a little over an inch between the two holes. and only slightly more for the 3/4. IS THIS ENOUGH????

[lastlight]

I think you need a few more inches between them otherwise the primary is going to be sucking air from the surface when it starts creating a vortex.

Not sure if this is an external or internal overflow but remember you can always drill a new hole from the side of an external or through the back wall into your internal and have it higher up so the top of the elbow/emergency is just below your overflow level. My water drops 1/2" into my overflow box since the water line is controlled by my emergency which always has a slight trickle going into it.

[ensquire]

Originally Posted by lastlight

I think you need a few more inches between them otherwise the primary is going to be sucking air from the surface when it starts creating a vortex.

Sorry Lastlight not quite following you here. When I was running it to test it, there was no noise, great siphon. The 1" drain has about 2" of 1 1/2" pipe sticking up and the 1/2 emerg rises to about halfway up the overflow teeth. there was no vortex at all, ran great like that for 3 days. Only problem was I used a ball valve instead of a gate on the drain which I will change. Problem came when I blocked main and the emergency line seemed a little small.
So are you saying that if I increase the secondary emerg drain size it might cause the siphon to not work the same ?? Presently the two lines are only 1 5/8 apart. A picture would help and I can't post one till tomorrow to clarify this.

Originally Posted by lastlight

Not sure if this is an external or internal overflow but remember you can always drill a new hole from the side of an external or through the back wall into your internal and have it higher up so the top of the elbow/emergency is just below your overflow level. My water drops 1/2" into my overflow box since the water line is controlled by my emergency which always has a slight trickle going into it .

It's an internal ..Never thought about this possiblity, definately a workable solution if the other doesn't

Thanks and sorry for needing the clarifacation.

[reefwars]

doesnt matter how cose they are if you keep one alot higher then the other so for me my main drain was about 3-4" from the bottom of my over flow and my emergency was about an inch from the top or the "teeth"

imo a 1/2" drain wont keep up to much so you will have to make it bigger, and your emergency should never see water untill it needs to in an emergency.a small trickle is fine but i try for dry.

i also made my emergency using a durso and i found it kept up well if not better but i had all 1 1/2" plumbing and 1" for my return lines.

cheers

[sphelps]

You can try using the smaller drain for the main and the larger one for the back up. Make both as large as possible by using thinner bulkheads if possible (although I'm not a fan of the thin ones)

Also an alternative for the back up is to use the smaller drain but use a larger diameter pipe than the bulkhead (if 1/2" bulkhead, use 1" riser pipe) in the overflow to slightly increase the amount of water flow it can handle. You can also use larger pipe below the back up bulkhead as well. This will eliminate most of the pipe friction and increase flow.

Lastly just throttle back your pump to match what your drain can handle.

I would use one or more of the above methods over re-drilling the tank.

[Parker]

*EDIT* What he said /\.


Another option is to throttle down your return pump to match the flow rate of your smaller drain It will slow down the amount of flow through your sump which some claim to be better anyway.

[The Grizz]

Originally Posted by sphelps

You can try using the smaller drain for the main and the larger one for the back up. Make both as large as possible by using thinner bulkheads if possible (although I'm not a fan of the thin ones)

Also an alternative for the back up is to use the smaller drain but use a larger diameter pipe than the bulkhead (if 1/2" bulkhead, use 1" riser pipe) in the overflow to slightly increase the amount of water flow it can handle. You can also use larger pipe below the back up bulkhead as well. This will eliminate most of the pipe friction and increase flow.

Lastly just throttle back your pump to match what your drain can handle.

I would use one or more of the above methods over re-drilling the tank.

Agreed

[ensquire]

Originally Posted by sphelps

You can try using the smaller drain for the main and the larger one for the back up. Make both as large as possible by using thinner bulkheads if possible (although I'm not a fan of the thin ones)

Also an alternative for the back up is to use the smaller drain but use a larger diameter pipe than the bulkhead (if 1/2" bulkhead, use 1" riser pipe) in the overflow to slightly increase the amount of water flow it can handle. You can also use larger pipe below the back up bulkhead as well. This will eliminate most of the pipe friction and increase flow.

Lastly just throttle back your pump to match what your drain can handle.

I would use one or more of the above methods over re-drilling the tank.

Some very viable options Thank you . But I did spend like 100.00 on various diamond bits and am dying to use them .
But seriously Ill see if I can upsize the pipes on both sides of the emergency and test that out.
Since I have tirn everything down again and can't test third idea out, my question is this.
When we throttle pumps down with a valve , does this not make them noisier ??
I will start a build thread to carry these ideas on with.

[sphelps]

Originally Posted by ensquire

my question is this.
When we throttle pumps down with a valve , does this not make them noisier ??
I will start a build thread to carry these ideas on with.

I depends on the pump and the quiet ones do sometimes make more noise with more head pressure but not always. In general a pump shouldn't be any nosier but different people have different results. When you close a ball valve it just increases the head pressure which is the same as lifting your tank higher above the sump. In addition you pump should use less power with more head pressure.

With the tank already assembled and already drilled I personally wouldn't try and drill a larger hole on top of a smaller hole unless it was absolutely necessary, and I've drilled a lot of tanks before.

[ensquire]

Thanks sphelps , I have to order a few fittings etc, as usual this isn't just done by driving to local store. LOL Good thing about it is that it gives me a chance to evaluate my options and no rushing into anything.
I will take the opportunity to paint my stand and move it to my office.
At this point I'm going to increase the pipe on both sides of the bulkhead and play with the outflow and see what that does for the situation.
I am moving everything else over to a build thread here :
http://www.canreef.com/vbulletin/sho...996#post596996