main drain and skimmer

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  #1  
Old 06-27-11, 10:54 AM
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main drain and skimmer

Hello all,

For some time now, I wanted to get a 50/50 mix of skimmer and main drain on my 60000L inground pool. It seems like pools today are circulated like this.

Anyways, I just got around to tinkering with it recently, and I have found a few things out.

The MD on thr pool is plumbed into the bottom of the skimmer, meaning there are two ports in the bottom. The other port is the return to the pump.

Here's a pic: http://i1132.photobucket.com/albums/...s/DSC00516.jpg

As you can see in the picture, the moveable flap which I believe is called the trimmer cover/plate, is completely covering the MD port. Also outlined in the picture, are several positions which are marked by the black ticks. What you do is loosen the plate, and move it inline with the marks.

I was instructed to move the plate to position 2 or 3, and drop the vacuum plate in. Apparently this would get the MD working. Well it worked, with some problems. I put the plate in the MAX SKIM position so both holes would be wide open. Why? Just imagine that the plate was in position 1, 2, or 3 as outlined in the photo. If it was in those positions, the return port is covered slightly. That doesn't make sense to me. Why would you have the return port covered? Don't you want full force going back to the pump?

Well back to what happened. At first it seemed to be working. Then all of a sudden, a small vortex was created, causing air to be sucked into the pump. Something is wrong here. Missing parts possibly? The skimmer is a Jacuzzi Model W.

A few diagrams are on the internet, but they are for the Model WC, WB, and WL. Although they seem to be all the same to me.

Hopefully somebody can help.
 
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  #2  
Old 06-30-11, 07:27 PM
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It sounds like leaving the port wide open like that allows too much flow through the skimmer, especially once the vortex started. Two things may have contributed to this: low water level in the pool and leaving the basket out of the skimmer. Just having the basket in the skimmer makes it harder for an efficient vortex to form, so if you left it out while you were testing the skimmer, that's part of the problem. Also, the water level should be near the top of the skimmer box. The weir insures that you get an efficient skimming action while allowing enough water to pour in to prevent air sucking. If the water isn't at least high enough to float the weir, it can't regulate the flow. If neither one of these conditions applies, you need to use the trimmer to reduce the flow. It seems like a crude mechanism--I think most people use three-way valves or separate ball valves to balance the flow--but it should work.

I normally run with both lines wide open, except while I'm vacuuming. Then I trim back the bottom drain to get more flow through the vacuum head. If you end up sucking the skimmer dry with both lines open, you either have an obstructed drain line or you're running too big a pump. Or both. If there's an obstruction in the drain line, and you need to throttle back the skimmer to compensate, then both lines would be obstructed, which can shorten the life of the pump. You could get a smaller pump, use a smaller return orifice or add another line and put an automatic cleaner on it or something like that.
 
  #3  
Old 07-01-11, 05:14 PM
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When I put the vacuum plate in for this test, the basket was always in place. Just today I tried it again, but the basket had a TON of leaves in it. I dropped the vac plate in, and hello, the vortex was created again!

After hours of studying diagrams for the skimmer, I've determined that the weir is in fact missing. It is suppost to be cylindrical, according to this diagram: http://www.poolsinc.com/images/parts/sc584.gif

I hope this is the part that controls the flow, and prevents air from being sucked in.

Now I want to throttle back the skimmer somehow, but if I move the trimmer plate, it will cover the return port. I don't know if covering the return port slightly is a good idea, but it just doesn't sound right to me. I could move it to throttle the MD, but the markings inside the skimmer don't have any positions in that direction. Just an FYI here, the pump is a Sta-Rite Duraglas P2RA5E-124L, which is 1 hp.
 
  #4  
Old 07-15-11, 08:15 PM
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By "return port" I assume you mean that opening at the bottom of the skimmer where the water goes back to the pump. (Usually "return" refers to the opening in the pool wall where the water jets back into the pool.) You have to partially cover that in order to throttle back the flow rate. That's how it works. Using a ball valve or gate valve does the same thing.

A 1 HP pump is probably not too much, assuming you have a 1 1/2" drain line, skimmer line and return line. That's what I have, and I have a 1.5 HP pump. It's way too big for my pool, but it only sucks air down the skimmer if I shut off the main drain ball valve when the water level is pretty low. I have a 1" orifice in the return eyeball.

I can't help thinking you have an obstruction in your drain line somewhere. If there's any way you can turn off each line, and you have a pressure gauge on your filter, you should develop the same pressure for each circuit when you shut the other one off. If one or the other develops a lower pressure, that line is obstructed. If you have a really old pool, it may have an iron drain pipe. These can rust and expand inwards, choking off the flow, but if that's the case, you'll also be seeing rust stains. If you do the pressure test and suspect an obstruction, try to get your hands on a waterproof borescope and see if you can see anything, or just see if you can get a snake to go through it.

I'm still not sure I understand how this thing is plumbed. You say there are two ports in the bottom of the skimmer. This is common, but usually only one is connected. If the second one is connected, it's usually just connected to the same line and just allows you to vacuum with out disabling the skimmer. If that's how yours is, the trim plate won't let you control the flow because it opens up one port when it covers the other. There should be a plug or a cap to put on the vacuum port when it's not in use. I believe this is #18 in your picture, but from what I see in your picture, your vacuum plate is missing, and a 1 1/2" threaded plug should work. If this doesn't make sense, you might need to draw a picture of what's connected to what.

The WB, WC & WL did indeed have a cylindrical, floating weir. Your picture doesn't show it, but there should also be an angular weir stop too. But there was a fourth widemouth model called the WWFL, which had a more conventional flap weir. I don't know how you'd tell what model you have, but you could look for the lugs a flap weir would snap onto. If you find them you might be able to find a standard replacement in the right size. If not, I'm afraid you're out of luck. You can still find the floating weirs around, for $50 or more, but the stops aren't available anywhere
 
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