Valve between pump and filter.

Like many, my pump is too big and I have a sand filter, which doesn't filter much at all. I am using DE in my filter, and that helps, but I also installed a ball valve between my filter and pump. The intention here is to restrict flow and decrease the filter PSI, hopefully allowing it to filter better.

What I have found is it works well, and I have very precise control over the pressure and flow at the returns. I also have great control of my suction side auto pool vacuum, which tends to want to climb out of the pool and cause the pump to cavitate. I have noticed the filter actually capturing the finer dirt and silt that used to get pushed through before.

My question is can I cause damage doing this to the pump or something else? Is this a good idea? I have also considered replacing the pump impeller, but with this setup I have a lot of control, like a variable speed pump. Thoughts?

I suspect you're going to burn out your pump motor faster and possibly increase your electrical usage. A lower capacity impeller or a two-speed motor would be a better solution.

Or a bigger sand filter. If it's a 1.5 hp Superpump or other IG pump you probably should have a 250-300 lb sand filter.

Ok, that's what I was wondering. My filter normally runs at 16 PSI, and with the ball valve I drop that to about 12 PSI and that seems to work well, but if I burn out my motor I'll be wishing I had upgraded the pump or filter. I was looking for the cheap fix.

I dunno. But you MAY be able to lower the speed of the motor with a transformer. I don't know how well or safely that would work, but that would be like a 2 speed pump. Still, it could burn it out as well. Have to find an expert on electrical motors.

I have often wondered if you could use a simple rheostat to control the speed of the motor, like any other electric motor used in electronics. Heck, even my electric chain saw runs faster or slower depending on how far I pull the trigger.

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Originally Posted by swimdaddy

My question is can I cause damage doing this to the pump or something else? Is this a good idea? I have also considered replacing the pump impeller, but with this setup I have a lot of control, like a variable speed pump. Thoughts?

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Throttling valves are common in the water distribution industry and are not a problem for the pump or motor as long as there is some flow rate. A pump motor actually uses less energy and runs cooler when you restrict the flow (i.e. higher head loss). The down side is it is less efficient in terms of GPM/Watt-hr.

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Originally Posted by swimdaddy

I have often wondered if you could use a simple rheostat to control the speed of the motor, like any other electric motor used in electronics. Heck, even my electric chain saw runs faster or slower depending on how far I pull the trigger.

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However, that can potentially burn out an induction motor. Reducing the voltage on an induction motor increases current and slip so it does slow down the motor but at a higher current use so it can burn out the windings.

That is interesting that the pump actually uses less energy and runs cooler with restricted flow. I do find that the filter, for what it is worth, does a better job with less flow. Its an intersting game I play, dropping the PSI with the control valve and then raising it some with DE. I think I learned this year that I probably backwash too much. I got in the habit of backwashing once a week but if the pool looks good and the PSI hasn't risen there is probably no reason to do it.

I have abandoned the idea of the rheostat or step down transformer, sounded good though.

The valve works really well, small movements change the PSI a lot, very fine control. Is there an ideal PSI to shoot for for efficient filtering? I don't know what my flow rate is, but the return jet is strong, kids can use a noodle to shoot water a good 15 feet. At fully open, 16psi, with DE 17psi, I have been throttling that down to 10 or 12psi.

Mark knows more about pumps than I do, so his advice takes precedence over mine.

We've well-documented over the years what you have found: A sand filter filters better with less flow. Something about the dirt not being forced past the sand as easily. That's why I'd rather run it on Low (2spd pump) than High pretty much all the time. Thus a bigger sand filter does better for the same reason: More capacity for the same flow.

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Originally Posted by swimdaddy

Ok, that's what I was wondering. My filter normally runs at 16 PSI, and with the ball valve I drop that to about 12 PSI and that seems to work well, but if I burn out my motor I'll be wishing I had upgraded the pump or filter. I was looking for the cheap fix.

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I would recommend buying another filter, the same filter you have now and connecting them both into service. This will double the surface area of filtration whilst keeping reasonable sized plumbing into each. This is preferable to have to try and sell off your filter and buy a single one slightly larger. I would have put that down as the cheapest fix.

I must admit I am baffled by how you would plumb in 2 sand filters unless they are both side-mounts and you use a single multi-port valve for both, and then it would probably need to be a larger and more expensive one. Otherwise I don't see how you could do it with 2 top mounts because of the multi-port valves. I guess they could be parallel, but then EVERY function would need to be duplicated on each, especially back-washing and you'd need to shut one down, than the other.

Comparing Hayward top-mount sand filters (Pro-Series):
An 18" (150#) filter runs about $230.
One with 22" (200#) runs about $250.
And a 24" (300#) runs about $380.

So I fail to see how a second 18" filter is cheaper than replacing it with a 22" or 24" filter. Plus if the 18" can be sold, even for far less, it offsets the cost of the bigger filter.

I have plumbed in two filters using side mounts and dual multiports and also on others gate valves to separate as you say for back washing. Top mounts could still be done. Takes a little outside the box thinking. The costs are quite a bit different to over here so I see your point but for the size of the pool and pump increasing the area of filtration will bring the water quality up as is already noted by valving the pump flow down.

18" gives an area of around 0.17m but a 24" is only 0.29m (sorry my spec is in meters) at $380 for a 24" and assuming original sold at 50% $115 the cost would be net $265 and you'd still have the smaller filter area. It does seem big pumps and small filters are the norm in the USA compared to Europe.

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Originally Posted by Teapot

I have plumbed in two filters using side mounts and dual multiports and also on others gate valves to separate as you say for back washing. Top mounts could still be done. Takes a little outside the box thinking. The costs are quite a bit different to over here so I see your point but for the size of the pool and pump increasing the area of filtration will bring the water quality up as is already noted by valving the pump flow down.

18" gives an area of around 0.17m but a 24" is only 0.29m (sorry my spec is in meters) at $380 for a 24" and assuming original sold at 50% $115 the cost would be net $265 and you'd still have the smaller filter area. It does seem big pumps and small filters are the norm in the USA compared to Europe.

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Yes, it's incredibly stupid and something Ben Powell has been challenging for many years. You can see his tip "The Bigger Pool Pump Scam" on his other web site, PoolSolutions.com which he started 19 years ago. I don't know how old the article is, but it was there when I found the site in 2000. It has been a constant frustration for us over the years.

Filter prices definitely, like any decision, factor in. Here, the difference between a 150# (18") filter and a 300# (24") filter is only $150--less than ₤100 for essentially double the capacity. Plus for SwimDaddy's pool, 300# would EASILY meet his needs even with a too-big pump. And, if he can sell the old filter for $100, that's 2/3 of his cost differential between another 150# vs a 300#.

Personally, unless the filter is damaged, I'd go with down-sizing the pump and getting a 2spd. VS pumps are very expensive still, and if you do NOT have a good surge suppressor they'll get zapped. I don't know if they yet make the cut-off suppressors for them. These are sold for appliances and won't come on if you are having a brown-out (low voltage) which zaps electronics as badly as surges.

I have thought of getting another similar sized filter and plumming them in parallel, but decided it wasn't a good idea, more of a hassle. Have been scoping ebay for a larger 24 or even a 27 inch filter for next season.

I will also someday be looking for a VS or 2spd pump, but for now I think the filter is more of a priority. Maybe you all can confirm or dismiss my conclusions. When you vacuum with a suction side vacuum using a 2 spd pump, you use the higher speed, right? Doing that with my filter pushes the dirt right through. I can vacuum better with DE in the filter, but the filter is so small it clogs up pretty quickly (lots of dust and smoke where I am at right now). I hate vacuuming to waste because of wasted chemicals. My hope is that a bigger filter with or without DE will allow me to vacuum through the filter.

Well, yes, a bigger filter should fix that. If you look at my sig, the T210 is a 22" 200# sand filter and you can vacuum on High without a problem. But the 200# filter is really the smallest I can use with this pump. Had I known in 2002 what I know now, I would have gotten the 250# or 300# filter. But it's OK. I really think you don't need anything bigger than 300#, max. Even that's overkill but....I'm betting you won't have anymore problems. WaterMom, our other mod, has a 300# sand filter with, I believe, a 3/4 hp pump for about the same size pool as you and has no problems with it.

Thanks Carl and Mark for all the great info. I have to say I am not looking forward to next season without this forum. I am glad it was here for the 2 seasons I have had my pool open, I think I can handle most things now on my own with the knowledge I have gleaned here. At the moment, I think I will be able to swim 1 or 2 more weeks before things get too cold and I'll have to close. Why does the pool have to look so inviting when it is freezing cold!

It's a mystery! (Of course the colder it is, the more it inhibits algae growth so it stays clearer...)

Winter approaches. So sad!!!!

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Originally Posted by swimdaddy

I have thought of getting another similar sized filter and plumming them in parallel, but decided it wasn't a good idea, more of a hassle. Have been scoping ebay for a larger 24 or even a 27 inch filter for next season.

I will also someday be looking for a VS or 2spd pump, but for now I think the filter is more of a priority. Maybe you all can confirm or dismiss my conclusions. When you vacuum with a suction side vacuum using a 2 spd pump, you use the higher speed, right? Doing that with my filter pushes the dirt right through. I can vacuum better with DE in the filter, but the filter is so small it clogs up pretty quickly (lots of dust and smoke where I am at right now). I hate vacuuming to waste because of wasted chemicals. My hope is that a bigger filter with or without DE will allow me to vacuum through the filter.

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I do that hassle quite a lot, and there are good reasons why but with some I use a single large filter as one extra valve here or there even with labels is to much for some. The advantages are two 19" filters can often be nicely tucked away rather than the larger single filter. You have to go to a 30" to get just over the same surface area as two 19" filters. Two filters will have twice the laterals and plumbing supply them lowering the pressure drop. With a small single speed pump you can shut off one filter and use the pump to backwash one filter at a time getting a good flow rate for cleaning. You still get more than enough flow for vacuuming with a 0.5hp pump, look at my signature, see how big the filtration pump isn't but it gives good flow.
The idea from manufactures of high rate filtration means that a lot of pool builders install or supply, based on the Maximum flow they think they can get, that requires a maximum HP to try and achieve it which results in the maximum electricity bill.

I agree with Carl, a pump swap is the most desirable but I would still increase the filter size to suit the size of the pool. Yes more capital outlay now but big savings on electricity long term will quickly dwarf the spend.