Pump too big?

[lebaige]

Earlier today while vacuuming I noticed dirty water blasting out of my return line like there wasn't even a filter there. My first inclination was "hrm, something must be wrong with the filter valve". However, I'm starting to wonder if my pump isn't just a bit over sized. What SHOULD I be using?

Pump: Doughboy Power Pak II 1.5hp
Filter: Doughboy Media Master Model 1600
Pool: 24' AG ~ 13k gallons

 

[duraleigh]

Earlier today while vacuuming I noticed dirty water blasting out of my return line like there wasn't even a filter there. My first inclination was "hrm, something must be wrong with the filter valve". However, I'm starting to wonder if my pump isn't just a bit over sized. What SHOULD I be using?

Pump: Doughboy Power Pak II 1.5hp
Filter: Doughboy Media Master Model 1600
Pool: 24' AG ~ 13k gallons

Well, you'd have to know the flow rate of your filter in gpm and then find the pump curve to see how many gpm it's producing. That said, Doughboys have a reputation for overpowering a filter with a too big pump.

However, I'd look for something wrong with the filter....I assume that's a cartridge. Check for damage to the cartridge or something not fitting properly in there....I'll bet that's where the dirt is coming from. Sorry I can't be more specific....I know little about carts.

 

[lebaige]

It's a sand filter actually .. 16", holds 150lbs of #20 sand per the manual. Unfortunately Doughboy is very tight lipped with actual useful specs, i.e. GPM ratings on their filters and pumps.

I'm contemplating replacing the pump anyway as it's leaking internally somewhere and I don't really feel like dismantling it in a desperate attempt to find the problem. Anyone care to recommend a reputable brand to look at that isn't such a miser with their vitals?

 

[duraleigh]

Sand? Now we're talkin' You need to inspect your laterals. Dirt has a tough time getting through a sand filter unless one (some) of the laterals are damaged or the multiport valve is never directing the water into the filter. There's some other, more obscure reasons but the laterals would be my best guess.

 

[duraleigh]

Sand? Now we're talkin' You need to inspect your laterals. Dirt has a tough time getting through a sand filter unless one (some) of the laterals are damaged or the multiport valve is never directing the water into the filter. There's some other, more obscure reasons but the laterals would be my best guess.

 

[lebaige]

I'm not sure I know what you're referring to when you say laterals .. I contemplated disassembling the valve on top to see if it is functioning properly but have not yet done it as I'm not really sure what I'm looking at. I suppose it's one of those things I'll just have to bite the bullet and do and learn as I go.

 

[duraleigh]

My first assumption is you have backwashed and gotten a subsequent pressure drop after doing so. verify that.

If your water is flowing correctly, the valve at the top is probably not the issue....probably.

The laterals are near the bottom under the sand and you will carefully need to remove the sand and inspect them.

Just about any Manu. Web site will show an exploded diagram of a sand filter and it will rapidly make sense to you. If you do this, you certainly can save the sand for reuse. It is not a quick job but it sure sounds like that may be the issue

 

[Ohm_Boy]

Here's an image I stol.... er.... borrowed from Hayward's website. It's an exploded diagram of a Hayward S310S above-ground sand filter. I took the liberty of highlighting the laterals.
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[lebaige]

Well, I disassembled the top valve .. everything seems to be in working order, the valve gasket is in good shape. I've been playing with forcing water through it and I am wondering if it's not just building up enough pressure to blast past that gasket and go right out the return, but I can't recreate it so I guess there's not much more I can do on that front. I did tighten the lid back down onto the valve body as well as I could to ensure a good seal.

Here is the schematic for the filter I use .. it's dark outside so I'm not going to mess with it until the morning. They refer to the portion in the bottom as the "underdrain", which I would imagine houses what you are referring to, although the diagram is not clear.

Oh .. as far as backwashing goes .. that is one of my concerns. I'm getting around 15 PSI under normal filter operation. This does not seem to be changing at all unless the SKIMMER sock gets significantly clogged. The filter itself does not appear to be building up pressure. I backwash for a couple minutes and nothing really changes. I don't see much dirt coming out the waste side either. For as dirty as my pool has been, there should be all sorts of crud.

 

[JasonLion]

I have had a problem somewhat like yours that turned out to be caused by water bypassing the filter because of problems with the main valve. If you see sand coming out of the return then it is very likely a problem with the latterals, but if you see the same kind of crud you get in a skimmer sock coming out of the returns then it is most likely a problem with the main valve.

 

[Rob]

I had a really similar problem, and found the same thing as the post above.

What I did was put a skimmer sock over one of the returns to directly capture the junk coming from the filter, turned out to be not sand but basically dirt and other stuff that should have been filtered.

I took apart the filter and found the top valve had cracked in half and rotated, allowing some "waste" water to be shot out the returns.

That being said, my sand filter is much simpler then the one you posted, so your issue may be similar but being caused by something different (if that makes any sense)

 

[lebaige]

Well .. I've more or less decided that the filter is fully operational. I can find nothing physically wrong with it that would cause the sort of problem I'm having. Apparently Doughboy Media Master filters don't use traditional laterals, but rather some sort of one piece underdrain.

The only other possibility I can think of is the pipe that leads from the multi-valve to the underdrain is not mating properly and is allowing water to flow directly back into the return. It's not broken or damaged as far as I can tell however, so I'm not sure why that would be.

I did notice the sand itself seems like it might be a bit low .. if I stick my hand down into the tank I don't run into it until I get about a foot or so down from the top. Is this normal?