Used sand filter - avail. options & your recommendations

[y_not]

That's nonsense. The valve will fill up with very little flow rate. Besides, the multi-port valve does not fill up with air when the pump is shut off anyway. At least it shouldn't so it is always filled with water. But you have to ask, so what if the valve doesn't fill with water? What difference would that possibly make? The important thing is to flush the dirt from the sand. His comments just don't make any sense. I think he is making it up.

My thoughts exactly Mark.
I just placed another call to Pentair to find out what happened to this supposed "spec sheet" he got these claims from. He says he got it out of their catalog, but it's nowhere to be found in there.
The rep I just spoke to, Gayle IIRC, says I need to talk to Carl Popma in WI. He's their nerd apparently.
She did confirm that it only comes /w a 2" multiport, so that blows holes in what he said right there.

You do know we shouldn't ask such silly questions of.... well, you know.
You might not like the answer after all. LOL

My favorite here thus far is...

"DE in a sand filter will ruin it" .... "Sand has to be changed every 2-5yrs cause it rolls around just like in the ocean."

*Places head in hands, beats forehead repeatedly.*

UPDATE:
I just spoke /w Carl Popma @ Pentair. He confirmed, as you have said, that maximum flow of a sand filter is 20GPM/SQ ft. to avoid channeling, recommended flow is 15GPM/SQ ft. and minimum is 10GPM/SQ ft. He confirmed that any old flow rate, even a trickle will do for just daily filtration, but for backwashing, in order to achieve proper disturbance and agitation (I think he used that word) of the sand bed so it'll clean properly, you should target to the middle @ 15GPM. Which for this filter /w 4.9SQ ft. of surface area would be 75GPM. The low end @ 10GPM would equal 50GPM minimum backwash flow rate. He said if you can only do the minimum, it'll still work, it'll likely just require longer backwash times in order to get it all clean.

Does that sound about right?

Head loss & required pump..

Apparently the headloss of the filter, which I forgot to confirm /w Carl, is 37ft/head.
What is typical headloss of the usual AGP 1-1/2" hose setup? 10ft, 20ft... more?

Best case scenario, at 47-50ft of head on a Pentair Dynamo 1.5HP stock, I'm looking at 15-20GPM flow rate. YIKES!!!! That's a weeny pump.
The Hayward Power-Flo Matrix isn't much better @ 27GMP for 50ft/head.

I see that the highly recommended Pentair Whisperflo 2-speed @ 3/4HP will yield 70GPM @ 50ft of head, or 60GPM @ 60ft of head. That ain't bad.
But what's bad is it's almost a $600 pump, even after deal hunting, 2x the $$ of the Hayward.

Using the Dynamo as a booster pump?

Can I just plumb in 2 pumps?
IE. Buy a new Hayward Matrix for about $230 bones (found me a deal), then plumb it alongside the Pentair Dynamo that comes /w the pool. Then only run the Hayward on low for daily filtration, then when it's time to backwash, kick on both pumps at full speed.

Will this work?
Or will I get even more headloss from this setup?
Even considering that the filter has a 2" MP valve union, allowing both of these 1.5" pumps to merge into a 2" pipe via a step up at the pump head. It's probably incremental, but hey, an idea.

 

[y_not]

Back to the question of a Ford Explorer hauling it all.

Well, between then & now, the Exploder's forward engagement clutch has taken a turn for the worst & the bands are beginning to slip when engaging from a dead stop to start. Once she gets moving, she's fine. So it's resigned to light duty till I can find an affordable rebuilt to put in it. I'll be using another vehicle, a 91/92' S15 Jimmy. I'll take both & haul light things in the Exploder, the rest of the heavy lifting will be done by the GMC.

Depends on a lot of variables, what all are you getting, what tools and equipment you have to take if you have to disassemble the pool. I'd figure at least 2 trips. I used a Dodge Durango and a 3 horse, horse trailer, but I was going 150 miles taking all sorts of tools, a wheel barrow, large shop vac and a dolly...... The rails, caps and uprights just didn't seem to pack into a tight space so they sort of spread out.

It doesn't sound like I'm hauling anywhere near as much as you had to. Maybe because there's no tool shed, non-resin pool so things stack extremely compact.

Sounds like you had a lot of fun taking her down & loadin' her up.

The rolled up wall was heavy, glad I didn't have to lift it into the Durango.

We'll have 3-4 grown men to lift it, so we should be good. I have hauled worse, although it looks rather springy and unruly. LOL
But we'll whip it into shape.

I was wore out by the end of the day. Just me, the DW and 2 preschoolers to disassemble and load it all.

WOW! I bet, lots and lots of sweat. I bet the rest of the gang was super tuckered out too. Even the preschoolers proportionately. They can be little troopers though!
Not to mention, then you had to; excavate, prep the ground, build, setup, clean the parts, lay the liner, plumb, etc...... I'm not looking forward to that part. It'll be fun, but wowwwiiieee!! I can see some motivational problems /w that one.
Aaaaallll the dirt we're going to have to remove and no way to fit a pickup back there, best case scenario's going to be if I can get a hold of a 6-wheel Gator to use for hauling dirt in & out, or a an ATV /w a trailer on it. We're in suburbia and it's all built up around us, not like it was when we 1st moved in, where, shoot, we could have bribed the super nice development workers to dig it for us. HEEEEE
But the good news is, once I get started on a project, I run & run & run until the day's done and I'm flat out DEAD!! The problem is convincing myself to get back out there the next day & the day after that. HAHA

 

[mas985]

UPDATE:
I just spoke /w Carl Popma @ Pentair. He confirmed, as you have said, that maximum flow of a sand filter is 20GPM/SQ ft. to avoid channeling, recommended flow is 15GPM/SQ ft. and minimum is 10GPM/SQ ft. He confirmed that any old flow rate, even a trickle will do for just daily filtration, but for backwashing, in order to achieve proper disturbance and agitation (I think he used that word) of the sand bed so it'll clean properly, you should target to the middle @ 15GPM. Which for this filter /w 4.9SQ ft. of surface area would be 75GPM. The low end @ 10GPM would equal 50GPM minimum backwash flow rate. He said if you can only do the minimum, it'll still work, it'll likely just require longer backwash times in order to get it all clean.

Does that sound about right?

Yes, that makes a lot more sense.

Apparently the headloss of the filter, which I forgot to confirm /w Carl, is 37ft/head.

Filters have a flow rate dependent head loss like everything else so was that at the design flow rate?

What is typical headloss of the usual AGP 1-1/2" hose setup? 10ft, 20ft... more?

It depends. Head loss in plumbing is flow rate dependent. But most AGPs will have a plumbing curve that follows a parabola like this: Head (ft) = 0.0167 * GPM^2

So the head loss depends on the pump and plumbing and you have to solve two equations in two unknowns (GPM & Head).

I would not put a IG pump on a AG pool. There is no reason to. AG pumps will cost less to operate and there are some that can deliver the flow rate needed for backwashing because most of the plumbing is bypassed in backwash mode so the head loss drops significantly. I think a Dynamo 1 HP pump can easily deliver 50 GPM in circulation mode and 80 GPM in backwash mode.

But this might be a little late in asking but that filter seems way too big for that size pool. I know we always say bigger is better but in this case it is way more than what you need. Is the current equipment failing in some way?

 

[y_not]

Apparently the headloss of the filter, which I forgot to confirm /w Carl, is 37ft/head.

Filters have a flow rate dependent head loss like everything else so was that at the design flow rate?

I don't know, I'm guessing it's somehow wrong, in the sense of assuming maximum flow rate. Which is like, yeah, right! I'll have to... once again.... check /w Mr. Carl. LOL
I'll let you know.
I'm assuming I should find out what the head loss curve is is for the 50-75GPM backwash rate?

What is typical headloss of the usual AGP 1-1/2" hose setup? 10ft, 20ft... more?

It depends. Head loss in plumbing is flow rate dependent. But most AGPs will have a plumbing curve that follows a parabola like this: Head (ft) = 0.0167 * GPM^2

So the head loss depends on the pump and plumbing and you have to solve two equations in two unknowns (GPM & Head).

I hate algebra.
So you can't know the GPM /w out knowing the head, but you can't know the head without knowing the GPM?? :?
I don't need it "solved for me", but I'm thoroughly lost on that one. I'll give you a hint, my brain is abstract, so math absorbs funny /w me.

I would not put an IG pump on an AG pool. There is no reason to. AG pumps will cost less to operate and there are some that can deliver the flow rate needed for backwashing because most of the plumbing is bypassed in backwash mode so the head loss drops significantly.

How does it bypass it? You mean inside the filter, there's a less restrictive route taken? I presume the return pipe leaving the filter, going back to the pool also removes a significant amount of head? I guess I was thinking most of the head would be at the suction side, then at the filter, forgetting about the return line.

I'd prefer not to have to buy an IGP pump, they're 'SPENSIVE!

I think a Dynamo 1 HP pump can easily deliver 50 GPM in circulation mode and 80 GPM in backwash mode.

Yes, assuming there's no more than 10 or 20ft. of head in backwash mode. According to the chart that is.

But this might be a little late in asking but that filter seems way too big for that size pool. I know we always say bigger is better but in this case it is way more than what you need. Is the current equipment failing in some way?

I currently have the pool in my sig. But I just bought/am buying a 27' Esther Williams/Johnny Weismuller pool off CL. 52" sidewalls and a 6-7ft deep end, depending on what I decide on a liner & cost. It comes /w the Dynamo which sounds beautiful on a quick dry fire. It also has a filter, but it's microscopic. 150lb /w a max flow of 35GPM!!!
I know when I go to pick it up this weekend and take it apart to clean it out for transport, that I'll find channeling. It's just too much pump for such a tiny filter. He had a loooott of trouble keeping the pool clean and had to backwash it something like every day or 2. It's no wonder!

So I have to replace the filter, or at least get another smaller one to plumb alongside it. Due to the cost of used filters "here" and head loss, I figured why not go with the TA100D 600lb filter. It's only $100, plus a bit for gas. It'll be the same cost as a used small filter, which will still be too small for what's available here, and I won't have to backwash this one much. So I'll save on chemicals.

That's the logic behind it all.
Flawed and silly as it may seem.

That's me. Flawed & silly and hairbrained plus crazy as a pole cat. :jocolor:

 

[mas985]

Ok, thanks for the background. That makes sense.

But to your other questions:

I'm assuming I should find out what the head loss curve is is for the 50-75GPM backwash rate?

No, it really isn't necessary. I pretty much can guess the head loss in both cases. But it will depend some on the layout of the new pool plumbing (i.e. pipe size, lengths, etc).

So you can't know the GPM /w out knowing the head, but you can't know the head without knowing the GPM??

Right, which is why you have to find the intersection of the plumbing curve with the pump curve. That is operating point. But first you have to determine the plumbing curve from the equipment layout. Pump head curves are published so that isn't so much of an issue.

How does it bypass it? You mean inside the filter, there's a less restrictive route taken? I presume the return pipe leaving the filter, going back to the pool also removes a significant amount of head? I guess I was thinking most of the head would be at the suction side, then at the filter, forgetting about the return line.

When back-washing, the plumbing post filter is bypassed.

Also, in most of plumbing systems, head loss is usually equally divided into three parts: Suction side, pad equipment, return side. This can vary by quite a bit but again it depends on the layout. If I had an exact layout of the plumbing including all fittings, valves, other equipment, etc, I could more accurately determine the head loss in the plumbing.

Yes, assuming there's no more than 10 or 20ft. of head in backwash mode. According to the chart that is.

Actually, the operating points are as follows:

Filter Mode: 48 GPM @ 39' of head
Backwash Mode: 76 GPM @ 24' of head

These points are located on the B&C head curve here: