Drilling for bulk heads help - 75 gal

I have a 75 gal, I am looking to drill 2 hole in the back for bulk heads.. either of a closed loop or a for my returns..

Cyan is my current setup
Red is the holes id like to drill
Green is a possible 3rd hole?


BUT.. Few questions

#1 Would I have to drain my tank completely? Or just like 60%ish of the tank? I mean it is all running now, I dont have any fish or anything.. jsut 2 corals thats it..

#2 How hard is it? Ive read/heard people say its really easy to do. just use lots of water when drilling and a diamond bit.

#3 What size do you guys recommend for the hole? I'm looking at doing [STRIKE]1" bulk heads[/STRIKE] - 1.5" Bulk heads

 

I dont have a definitve answer on this, but here's how I'd make that determination.

Find out what is the amount of water flow through the system you want to achieve? With a DT I believe that up to 50x tank volume/hr is ideal for SPS and LPS per the information I've read on the ecotech site. So, given that the amount of flow through your system should be 3750 gph.

Now we determine the maximum amount of flow by diameter of PVC pipe that will support that kind of flow. For 1.25" PVC it will allow for 3750 1.5" offers 4600 gph at the same pressure, which is roughly 100 PSI. I'd opt for 1.5 as this will be at a reduced pressure to achieve the same flow rate. Now that we have two returns we can reduce the diameter to say 1" and still have even less pressure per pipe.

So, I'd go with a 1.5" bulkhead, which will allow you to insert a 1" piece of PVC on the slip end of the bulkhead.

Just my $.02 from a n00b. Keep in mind I have no idea what I'm talking about.

If this is wrong my next suggestion is potato.

Have you considering a SQWD for changing flow patterns in the tank?

 

Thanks for the info, no worries I'm just a n00b here too.. xD

Umm yea I'm looking at it more and more. Im going to go with a 1.5" bulk head.
Also, Thanks for the SQWD idea, I'll have to look in it. It looks very interesting. I've only seen like Wavemakers, but that is cool.

I thought the next answer was tomato? I got it all wrong D:

 

As for the drilling. I would definitely drain the tank 100%. In the event of a worst case scenario the tank could break or shatter. That water would be everywhere. Not worth it IMHO.

Can't answer anything about drilling, inhaventndone it personally. Info understand it to be relatively simple. Just go slow and evenly with lots of cooling and you should be I'm the clear.

 

I have never attempted to drill a tank with anything in it, or where I was not drilling straight down, so I can't say for sure how well it would turn out for you. I just see too many ways for it to go terribly. I know I wouldn't want little shards of glass floating around the tank...

Maybe someone else has attempted this and could advise.

 

I would definitely drain the drain the tank 100%. When you drill down through a tank you don't really use pressure, the bit does the work. With the tank standing up, you will have to apply pressure. I understand you can limit it, but too much pressure and it may shatter. the last thing you want is glass shards floating around in the tank. Are you positive the tank is not tempered glass. Remember just because it already has holes in it doesn't mean it's not tempered. If there holes were there from the manufacturer it may still be tempered. And as mentioned before I would use a 1.5" bulkhead.

I have a local shop here that has drilled 2 of my tanks. He did it for 25 bucks. Check around unless you really want to do it yourself.

 

That is basically what everyone is saying, Lots of water and go slow with very little pressure

 

Yea I'm prob just going to drain the tank. I just wanted to see if I could. And not have the hassle of taking the whole tank apart and everything

 

Im going to go with a 1.5" Bulk head, as they have more flow If i need them to.
Also the nearest LFS is 25 mins away? like 19 miles I think? So I would rather just do it myself. Im really hands on and more DIY. That way I can do it how I want.