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  • Results 1 to 15 of 15

    Thread: Total Dynamic Head / Friction loss - Help please

    1. #1
      Enrgizerbunny is offline Senior Member
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      Total Dynamic Head / Friction loss - Help please

      I've looked at the head pressure thread and it's missing a LOT of charts on photobucket.

      I have an Aquaforce 2700 pump that feeds a DIY filter using a 55 gallon drum, which is pressurized. I want to move the filter and expand it to two drums (mech&bio).
      Here's the pump with it's flow chart:
      https://www.aquascapeinc.com/product...ling-pond-pump


      I'm trying to figure out exactly what I'm looking at for friction loss in this system and if my pump can do it.
      I will be pumping downhill slightly and then drums are 3' tall. Both filters will flow from bottom up, and I expect at least the first will end up being pressurized due to the flow.

      My questions are:
      Do I calculate TOTAL length of pipe/tubing+elevation or just pump->filter+elevation?

      I'm using a calculator like this - https://www.absolute-koi.com/tdh-calculator

      For the GPM input- should I enter the maximum output of the pump because that's what it's trying to shove through the pipes? I ask because I know if I pressurize both drums, I'll have extra pressure (more than gravity) on the return piping that will only have about +2ft elevation head pressure otherwise.



      I was quite confident the pump could do it, but when I entered total tubing length less any fittings and then added elevation it came up to a number that exceeds my maximum head pressure and I really don't want to make this move and then find out I need a larger pump that is hundreds of $$ extra. Help please.

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    2. #2
      batman is offline Senior Member
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      I did a quick check with all known values on the calculator you posted and it's way off. Do not use.

      DIY pressure filters in 55 gallon plastic drums typically don't work. Pressure flow to open DIY drum filters and gravity return much more reliable and easier.

      What is the maximum height water will be raised any where in the system measured above pond height?

      PVC pipe or ribbed pond tube? What diameter? Ribbed tube has much more friction.

      Total length of all pipe/tube?

      Total fittings and type?

      Fudge factor for filter resistance needed. SWAG
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    3. #3
      Enrgizerbunny is offline Senior Member
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      Quote Originally Posted by batman View Post
      I did a quick check with all known values on the calculator you posted and it's way off. Do not use.

      DIY pressure filters in 55 gallon plastic drums typically don't work. Pressure flow to open DIY drum filters and gravity return much more reliable and easier.

      What is the maximum height water will be raised any where in the system measured above pond height?

      PVC pipe or ribbed pond tube? What diameter? Ribbed tube has much more friction.

      Total length of all pipe/tube?

      Total fittings and type?

      Fudge factor for filter resistance needed. SWAG
      This thread contains pictures of my current filter, and it works quite well. The redesign will flow from bottom to top, in both barrels.
      https://www.koiphen.com/forums/showt...-it&highlight=



      HydroMaxx 100 feet x 1.5 Inch Black Flexible PVC Pipe, Hose and Tubing for Koi Ponds, Irrigation and Water Gardens. Includes Free 4oz Can of Hot Blue PVC Gorilla Glue! https://smile.amazon.com/dp/B0042LAL...GRDV8B5SSDXX28

      This is the flexible tube I'm using, then it'll convert to 1.5" PVC, probably ~8ft in total. Total flex tube length is looking like 60ft. Fittings should be 4 90s, 4 bulkhead fittings, a springless check valve, and a ball valve. Max elevation will likely be about 2.5ft above pond height because the new location is slightly below water level.

      Filter media will be 2-3 more layers of matala media and the second barrel will just have bioballs with oyster shells on the bottom. I'm considering swapping bioballs for K3 media. I may just get more bioballs.

    4. #4
      batman is offline Senior Member
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      Total head will be static head (height water raised) + plumbing friction head + a SWAG estimate of filter resistance head

      After all the plumbing questions are answered above use the equivalent length chart for fittings and add to total pipe length to get a total equivalent length of the system. Use the total equivalent length in charts or calculator for the pipe size and get friction head.

      This is for the pressure side of the system. If a gravity return is used from the filter it is calculated separately.
      Last edited by batman; 12-01-2021 at 08:45 PM.
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    5. #5
      batman is offline Senior Member
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      I looked at your thread and this is probably the best example of a DIY pressure filter in a 55g drum I've ever seen. I've had commercial pad pressure filters before and know cleaning pads are a quadruple PIA. If your new filter is in parallel with the old filter resistance will be 1/2. If in series 2X. This doesn't look like a high head system that would drastically reduce flow.

      Personally I'd convert to two 55g DIY SG filters in parallel and gravity flow back to the pond. Easy to see when they need cleaning and very easy to clean. Plus the bottoms can be occasionally drained of particulate between cleaning. Increase pressure pipe size to 2 inch. Use rigid PVC whenever possible.
      Last edited by batman; 12-01-2021 at 10:05 PM.
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    6. #6
      Enrgizerbunny is offline Senior Member
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      Batman,

      Thank you so much for your replies.

      Is the SWAG estimate calculation on the sticky thread?
      Pressure vs gravity doesn't much matter to me. I have pressurized because of the top-bottom flow and too much volume coming from my pump. The new location will be downhill from the pond slightly and still able to gravity return, but if I can put pressure behind it from the filter I'll have a much better flow me thinks. Thank you again for your information, I'll look at those calculations this evening. Parallel meaning pump feeding both drums, series meaning pump feeding first drum and return from second drum?

      My first filter was pea gravel in a 10 gallon barrel and it didn't flow at all. When I changed to bioballs it couldn't handle the pressure. Once I found these pickle drum with a screw on lid it's been swell for about 4 years now. I keep clear water where I used to have pea soup even with UV in the mix. Then I added a sponge eventually replaced with matala and it's been a great combination since then. My initial experience with the gravel is off-putting to me, but I know there's a way to do it if I choose that route. I think I'm going to stick with my current media for simplicity

      The new design I have is in series if I understand correctly.

      Pump flows to the first drum, goes through a bulkhead to 90 angled down to give a swirl below the matala to kick out any large particulates. After flowing through the matala, it'll be plumbed to the bottom of the second filter (plan being for the same swirl, but undecided because of the oyster shells) with bioballs/media, return will be a shower drain that is swiss cheesed around the edges, running a pipe down the center of the barrel and the discharge pipe will be at a similar height to the input. Both drums will have bottom drains utilizing the 1 1/4" bulkheads on the current filter.
      Last edited by Enrgizerbunny; 12-02-2021 at 06:16 AM.

    7. #7
      batman is offline Senior Member
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      SWAG (scientific wild a$$ guess) is just engineering slang to make the best educated guess based on relevant information already out there. For your example perhaps comparing to posted values on somewhat simular commercial types and adding or subtracting for size and internal details.

      Small pipe in the flow path will be a limiting factor that's easily changed. For ins and outs and internals I'd use minimum of 2 inch.
      Last edited by batman; 12-02-2021 at 10:11 AM.
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    8. #8
      Enrgizerbunny is offline Senior Member
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      I'll check it out, but I don't know if my pump will hook to 2" pipe.

    9. #9
      batman is offline Senior Member
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      Even if the supply from the pump is 1.5 inch having everything on the filter side at 2 inch will decrease back pressure. Common to see pumps with 1.5 inch connections with 2 inch pipe.

      Head pressure for 100 feet of 1.5 inch PVC pipe is several times greater than 2 inch at 2,000gph.

      With the equivalent pipe length of all fittings added to pipe used it's easy to reach 100 feet total.

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      Last edited by batman; 12-05-2021 at 09:07 AM.
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    10. #10
      Enrgizerbunny is offline Senior Member
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      I looked it up. It'll hook up to 2" pipe and I think I have the 2" adapter on the pump. Unfortunately I have to use flex for the overwhelming majority of my piping, but it's not the cheap ribbed flex, it's pretty smooth on the interior of that pipe. Allegedly the flex PVC will go straight to socket fittings on schedule 40 PVC, but I'm not sure I trust it. My current setup utilizes a barb fitting to adapt to the hard pipe.

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    11. #11
      Enrgizerbunny is offline Senior Member
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      After doing some research, I found some information on the flex PVC pipe. It says that there's 130 ft/head at 65 PSI. (it's 150 for 1.5"). Is there any way to use this information to figure out the actual head/100ft on this flex pipe or is it just a useless test number for my purposes?

      Link to the product:
      https://flexpvc.com/Guides/FlexHose.shtml

      Edit:
      I found a great chart on their website that I believe simplifies everything. Looks like you just draw a line through your known parameters and you get the unknown ones. I don't know if it's the same as Batman's chart, but I was looking for information specific to the flex PVC I want to use.
      https://cdn.flexpvc.com/graphics/hea...raph-chart.gif
      Last edited by Enrgizerbunny; 12-11-2021 at 06:03 AM.

    12. #12
      batman is offline Senior Member
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      Statement on Flex PVC claims only a 3% reduction. All fittings and bends also add resistance. Larger radius bends have lower resistance vs tight. A huge advantage of flex PVC is the ability to make smooth sweep bends. Keep straight sections as straight as possible.

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    13. #13
      stevek is offline Supporting Member
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      My experience follows closely with Batman's recommendations. Use 2 inch flex pipe for ease of installation , and use the SWAG factor after you do the preliminary calculation of head . My original pond builder used 1 1/2 ribbed flex pipe, and a submerged pump that was too small. I wasn't satisfied with the flow, and once I learned about dynamic head, friction loss, etc etc, from Koiphen , I redesigned my whole system and repiped everything myself. I think I had runs of 80 feet, so there was a fair amount of digging involved. I went with 2 inch flex pvc , and a much larger external pump, and everything worked out perfect. 15 years later, no leaks, and everything is still as I had hoped.
      Almost always better to SWAG the final estimate, and get a slightly larger pump than you think you need. Then, use a ball valve after the pump so that you can throttle down the volume if you need to. I was able to add a S+G filter into my system with some excess flow, and the ball valve allowed me to dial in overall volume so that my entire system is optimized.

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      Enrgizerbunny is offline Senior Member
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      Current plan is now to use 2" plumbing throughout the system for supply and return.


      Any thoughts on uni seals versus bulkheads for 2" pipe on a 55 gallon drum? I currently have 1 1/4" bulkheads that seem to work alright. I'm concerned about some information I've read about uni seals and UV exposure.

      Also what I've read I think I'll be able to adapt the flex straight to hard PVC with glue and won't need to use a barb fitting to make the switch. I'll have a ball valve on both sides of the filter, and at least a springless check valve on the supply side. I've had a power failure before that resulted in the vacuum collapsing the drum like a crumpled beer can. I was able to fix it by "inflating" it with the pump and then a couple days in the July sun and there were no leaks. It's been a couple years since that event and I'm trying to avoid a siphon situation during a power failure.

      Here's some pictures from my power outage:





      Last edited by Enrgizerbunny; 12-13-2021 at 11:43 AM.

    15. #15
      batman is offline Senior Member
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      Put a Tee on the return at the filter and add an air admittance valve. Closes on pressure but upon siphon (negative pressure) opens and allows air in. Valve must be vertical . Can be smaller pipe than system.

      Edit:. After more thought decided it's feasible to add directly to the filter to allow air in if pressure goes negative. Keep vertical and put valve slightly higher than filter. Could be mounted on screw lid. Reuse your 1-1/2 inch bulkheads.

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      Last edited by batman; 12-13-2021 at 07:04 PM.
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