Slow overflow?

[jgauthier]

Greetings everyone!

I'll try to get the the point quickly. I have an eshopps PF1800. It -was- attached to 1.5" PVC, down to 1" flex tubing. I was never happy with the flow. My pump can do 2200GPH. (The pf1800 is supposed to be able to do 1600gph, I believe)

Anyway, one of the bulkheads on the pump cracked, and I leaked water for weeks before I figured it out. What a mess. I was going out of town, and needed some stable filtration. So, I took 2 6' long pieces of 1" Flex tubing (the same I had before) and I just bypassed the overflow box, while retaining the safety of the box inside the tank. Holy COW. My flow was AMAZING! For the first time I ever, I cranked my pump all the way open, and it couldn't keep up! (I suspect that was because of the spray bar, but it's not important right now). So, I was thrilled with this. I felt like the tank filtration was awesome.

So, I decided to fix my eshopps with off the shelf plumbing, and redesigned it so I have 1.5" of flow the whole way. So, the bulkheads are 2", which then go into 1.5" flexible spa tubing, finally into 1.5" PVC into the wet/dry.

I was excited to see what my flow was like, because I assumed this was a limit of my previous design. After getting the box going... well, I am quite disappointed. My flow is no more than what it was, and my pump is probably running at 50% of its power. The pump can easily outshine the overflow.

Do you guys have any suggestions as to what is causing the flow to be slower than when I ran the two 1" flex tubes?

I considered the single siphon tube from the tank to the overflow to be the cause, so I put an additional one in place. It didn't help at all.
Now, I wonder if it's the "loop" that the spa tubes have under the tank. Each one comes into the tank, loops, and deposits itself into the wet/dry.

Otherwise, what? The sponges? I would think if the filter sponges slowed it down the overflow box would actually overflow itself from the siphon tube.

Anyway, interested in your thoughts.

Thanks!

 

[boldtogether]

The pre filter sponges could be slowing it down, the loops(come on, why?) and the tubes in the overflow. Not to mention the weir length of the overflow box itself. This is where some experimenting should be done.
First off, if the overflow is rated at 1600 and the return is 2200, I would get another overflow to make up the difference, or varify the actual flow into the tank, not what the pump says it will do. If its rated at 2200gph, is that what it will do at the head pressure of say 6'? If it will actually put 2200gph into the tank after it has pushed that water up and out of the sump, up and over the the edge, than get another overflow.
Second, I don't use the prefilter sponges on mine because I have mech filteration before the bio in my sump, and they get clogged and do exactly what you suggested, they cause the overflow box to, overflow, but in a bad way....you know what I mean.
Third, if the overflow box isn't wide enough to handle the modification of bigger bulkheads, it will only allow a certain amount to flow, no matter how big the drain.
The reason the 1" flex worked so well was because you were creating a siphon. The weight of the water was actually pulling water through the pipe at an accelerated rate. This is great for canister filters, the pump doesn't have to work as hard, but if the power went out the tank would empty itself. It is nearly impossible to get a pump to return exactly what a siphon would do anyway, but again, think about a power outage.

You can Google instructions on building a DIY overflow, but I personally find them to take up to much tank space. If you go the DIY way, you will be able to build it to handle just about any flow. For a bit more money, you could add another overflow box and it would look less obtrusive in the tank...just my opinion.
Bottom line for me would be to get as much flow from my return as possible. That for me has been: as straight as possible return lines, sized appropriately according to mfg spec., with no restrictions like nozzles or spraybars. This is because my return pump is not designed to operate under pressure. I have also made the drain lines as straight as possible so my overflow doesnt operate restricted in any way.
Good Luck.

 

[jgauthier]

Thanks for your input. My return is great. My overflow is slow. I understand what you are saying. When I had the two lines, the siphon was direct to the wet/dry. With the overflow, the siphon is much shorter, and then relies on the gravity flow instead of siphon.

I will think on how to make the best of both worlds. Thanks!