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I need a new pump/filter for my pool.
25000 gallon vinyl liner in-ground in the So. Cal. Desert. Current pump is a worn out 1.5 HP with a worn out 48 sq ft DE filter.
THe electric company gives a $250 rebate for a two speed pump ($30 for a single speed). So, two speed is the way to go.
Line to to/from pump are 1.5 inch.
I propose a 1.5HP uprated two speed pump and a 48 sq ft DE as replacements.
What say the experts?
So, no comments?
I am interested also, as I am going to purchase a new pump in the next couple days. Maybe we can get a few folks to mention their preferences and why. Thanks.
Hi, Mike/Scott,
When I built my pool, the consensus was to pump enough water to turn over your pool 2-3 times a day. (on high speed) (30,000 gal pool needs a pump to turn approx 75,000 gal in a 24 hour period......52 gal per minute.)
Then, choose a filter that is rated (in gpm) of at least 110% and maybe 130% of that 52 gpm....say, around 60-80gpm.
The trick will be in calculating total head of your pool so you can look up the curve of a particular pump and see if it satisfies your requirements.
I seem to remember an average pool has a total head of about 50 but I think there are others on this forum who have better info on that.
My pump and total head computed out to about 90gpm on the curve (1.5 full-rated) so I got a filter rated @ 140 gpm.
To summarize, compute how much water you need to turn, get an average idea of your total head, find a pump curve that matches that, get a bigger filter.......you're good to go.
Dave S.
I've kinda done that. The hard part is coming up with total dynamic head. SInce the pool exists, I cannot go out and figure out how many elbows and such are there. I don't have X-Ray vision. So, I went with the typical 40 to 50 feet of head. A 1 hp full rated or a 1.5 hp up-rated pump fits the bill, at least it does if I haven't screwed up something. Also, a 48 sq ft DE filter has about 1.5 times the needed flow rate, so I think thats the correct choice.Quote:
Originally Posted by duraleigh
I'm looking at a Hayward Super II pump or a Pentair Whisper flow. The exact model depends on whats on Southern California Edison's rebate list.
I'm looking at a Pentair FNS plus or a hayward pro-grid.
I think I'll also put in a rainbow in-line or off-line clorinator (model 300 or 320).
The most accurate way to determine head is to measure it.
What is your filter PSI? Multiply it by 2.31 to get return head.
Suction head you can get with a vacuum gage (Sears has them for $20). Multiply in mg by 1.13 to get suction head, then add together. Once you have total head you must scale it by GPM of the new pump. Unfortunately, it is an iterative process because GPM and head are dependent upon each other. I use a spreadsheet with hydraulics equations to solve for each.
For comparison, I have a 21,000 Gallon pool with 2.5" & 2" plumbing, filter, heater, spa and 1HP Northstar pump. From measurements that I took, my head is about 56' @ 92 GPM.
Also, if I had a bit more information, I could estimate head for you and what it would be with a different pump.
Current Filter PSI
Equipment list
# Suction lines, ~ length & dia
# Return lines, ~ length & dia
The rest I can guess.
Well, current filter psi is a bit of a problem. When I took everything out of service for the winter, "normal" filter psi after backwashing was about 4 psi. The problem is that I get crap for flow. The filter is a 48 sq ft stainless steel nautilus with pin-hole leaks and a leaky seal. The pump is a old bronze 1.5 hp aqua-flow, which I understand eats impellers. The system is shot, so any pressure reading I get is probably bogus. I can never get the filter psi over about 8.
When I bought the house, the pressure guage didn't work (I plumbed in an automotive pressure gauge just to get enough sensitivity to see if the system worked). The pump had no strainer basket and the pool skimmer had no basket. I took apart the filter and it was completely full of very brown DE. I replaced one grid, patched two more grids and several grids had internal stiffeners cracked and broken and I just left them. I only had two months of usable season left and knew I would replace things in the off season.
The suction line I would estimate at 36 + 18 + 10 feet or 74 feet. Its a 18 x 36 pool and the equipment is maybe 10 feet off the corner furthest from the skimmer. The return I would estimate at 10 feet as its a straight shot to the pool corner. All piping is 1.5" except between the pump and the filter, which is 2". Equipment would be a 48 sq ft DE filter a 1.0 full rated or 1.5 up rated pump and a in-line clorinator, unless something else looks like better match. The pump is intended to be two speed.
If you can provide some rational numbers, I would appreciate it. I plan to go down to leslies pools and order some stuff tomorrow morning. They are having a 20% off sale, so they are very competitive with an internet purchase. Right now we are looking at the hayward products, the 1.5 hp super II pump and the 48 sq ft FNS filter. I'm also considering pentair products, but leslie has less of a selection of that brand for sale.
If you only have 1 skimmer and 1 return line, your head will be quite high with a full rate 1 HP pump. I estimate over 70 ft of head which is mainly due to the 1.5" 75 ft of suction pipe.
The maximum recommended GPM for 1.5" pipe is about 42 GPM. If you go with a 3/4 HP, the head will drop to 60' @ 57 GPM. At 1/2 HP, the head will drop to 47' @ 50 GPM. These are only approximate since it depends on the pump type.
Here is a web site to help with pump sizing:
http://www.poolplaza.com/pool-pump-sizing-2.shtml
Basically your telling me that its about impossible to optimize my pool. If I go with a 3/4 hp pump, then I'm slightly overdriving my plumbing. I might be able to live with that, but then, on low speed, I'm basically moving not enough water to turn over my pool. Low speed is 3/32nd hp. Not much flow and thats a lot of water to move. I think I can get maybe 20 GPM or so at low speed, but since TDH goes down with the lower velocity, I have not idea what it is.
To turn over a 25000 gallon pool in 8 hours requires 52 GPM. Since I can only get 44 GPM out of 1 1/2 inch pipe, this is impossible.
Aparrently the 44 GPM comes from the building code requirement to not exceed 8 ft/sec in the pipe. A pipe can technically support the flow, but pipe damage can occur. Thus, I can exceed 44 GPM and the pump shouldn't cavitate or do evil things.
A better match is the 1/2 hp pump, but then I'd get essentially nothing out of low speed, if I can find a two speed pump.
The most correct answer is to add a second suction and return or convert to 2" pipe, both which are essentially impossible on an existing pool. I actually have a second return. That is intended for a pool cleaner with a booster pump. Since the pressure side head isn't a large contributor compared to the suction side, I don't think it would help much.
Hi, Mike,
Mas985 has given you some great info but you seemed to shuffle it aside maybe a little too quickly. Two thoughts come to my mind....Could you get your .75 2-speed pump (for the rebate) and run it on high all the time? Seems simple enough.
When you get your new pump and filter, could you replumb your booster pump line to become a suction line...or perhaps perform both functions if you use the booster pump.
I will also promise you can push more than 44gpm thru a 1.5"pipe without harm....been there, done that.
Impossible to optimize your pool? Optomize means doing the best you can....not perfection, but the best you can do with what you've got. I think you can improve your system markedly with a little more planning. :) :)
Dave S.
No, I'm not trying to push his information aside. I very much appreciate it. I agree that getting a downsized pump and running it on high most of the time is a rational plan.
The problem I see is that going too small won't allow me to get a decent turn-over rate.
I've been doing a little more research and it does appear that I can push a bit more flow that 42 GPH even though its not the best idea. Something on the order of 55 GPH or so.
The thought of using the booter line as a second suction line is very intriguing. That would be terrific if I can do it.
The port on the side of the pool is maybe 18 inches below the surface. Would this really work? BTW: The only reason I call this the booster/cleaner line is that what the previous owner called it and there is an unused booster pump in the pool house. He said he threw his cleaner away because it didn't work.
Can I have 2 1.5 inch suction lines and a single 1.5 inch return?
ALso, thanks everyone for helping me through this.
Hi, Mike,
I would envision the suction side plumbing something like this...two 1.5 lines, contolled each by a ball valve, coming from the skimmers and the booster line, teeing into a 2"line at least 12" long that goes into your pump. Even if you have to come back down to a 1.5 entrance into your pump, that 2' tee will reduce some turbulence and, therefore, TDH.
The downside is that you would have an open suction line on the side of your pool that could grab somebody and could actually be a little dangerous if, for some reason, you shut off the skimmer suction line. You can buy a little plastic guard to screw into that booster line which will greatly help, but not eliminate, that issue.
If you really wanted to get complex, you could tee off that booster line with some more plumbing so it could be controlled as a suction side or pressure side line. I doubt that's a great idea, but it could be done if you needed to.
Mike, if you can get 50gpm through there, that's 24,000 in a 8 hour period which I think gets you right about where you want to be. Others smarter than me may nix this whole idea but it seems to me it would work nicely.
Dave S.
I was thinking a standard Jandy 3-way valve that I would just use as a blend valve. Common plastic ball valves don't seem to last too well.
Also, I do plan to use 2" line on the equipment pad between all components. I'll use bushing as the pipes come out of the ground to get to 2". I will have about 2 ft to the pump entrance, so thats not a problem.
The biggest mechanical problem I see with attaching the two lines together is that they are not in nice positions for connecting together. Trying to minimize elbows will be a challenge.
I'd like some help from the experts too as I'm also looking to go with a two-speed pump.
16x32 foot in-ground w/ vinyl liner. 19,200 gallons before we put steps in the corner last summer.
All 2" pipe.
24" SplashPak Sand filter
2 suctions (only one running at a time) - 1 is 17' (skimmer) run and the other is 27' (vacuum). I believe each has 3 elbows before the 2 near the pump.
1 return is 24' with 4 elbows.
Thanks in advance!! Ken
Mike, will that valve allow you to have all the ports wide open simultaneously? I don't have any Jandy's..I know they're good quality...but I was thinking a 3-way was an "either-or" valve but not both wide open.
Anyway, I think you're on the right track. An extra 90 turn or so won't add much head and you're really gonna' cut it (head) back if you can get two suction lines going. Let us know how you end up.
Dave S.
Hi, Ken,
You'll get much more attention if you start a new thread. Much easier for folks to find and subscribe to.:)
Dave S.
Dave S.
I did a little more research and, while I found almost nothing about suction lines that are not drains or skimmers, apparently these types of lines are also used as dedicated vacuum lines. The thing is, that you are supposed to have special ports that close when a vacuum is not in use. I assume that is so you done suck up your nephew (or at least give him a big raspberry). I did not find any special covers to add safety. Withoutthat level of safety, I feel I cannot use that line as a suction. We run a day-care out of the house and thats too much liability unless a suitable cover exists.Quote:
Originally Posted by duraleigh
Hi, Mike,
Yeah, those nephews are a pain in the patoot!!!:D I do have a couple that could use a good raspberry, however!:D :D
I would not use that line with a day-care situation, either. The fitting I have seen is a small, plastic screw-in that would not offer adequate protection if, somehow, that opening became your only suction side water source.
(That's how John Edwards won his first big case and, eventually, started his political career)
A cover could be made perhaps, but with your liability exposure, I'd resign myself to the smaller pump. You'll have to run it a little more, but I think you'll still get satisfactory results.
Dave S.
Could you use something like item 34-215 on this page:
http://www.recreonics.com/fyi/wall_fittings.htm
Also, the 3-way Jandy valves do have the ability to position such that both lines are on.
Probably can't use that. It would have to fit a vinyl lined pool in a retro-fit application. That looks like it will only fit a new installation since its a solvent welded application.Quote:
Originally Posted by mas985
The question on the Jandy is not that it would open both ports, but would it open both ports fully and create no significant restriction. Two ball valves would create essentially no restriction, but its two parts and the valves are not as reliable from what I've read.
I have used a Jandy 3-way to fully open all three ports at the same time so it basically looks like a tee. The opening for each port is about the size of the pipe so restriction should be low.
The valve can be set up to rotate the off position through the middle port or away from the middle port. The later allows you to rotate the off position to where there is no port (opposite the middle port) thus allowing for all three ports to be open at the same time.