Stuff To Remember About Pools

My pool is finally about to be opened for the year. Even though this is something I do every year, it sometimes takes me a while to remember what I do each year to make pool-opening happen. I’m going to use this post to record some information I know I’m going to want to reference sometime in the future. And maybe you’ll find it useful as well.

If you already know a lot about pools, maybe go straight to the paragraphs in green. That’s where I’ve indicated some things I’ve learned most recently, which might be basics for others, but it took me a while to get to.

About My Pool

Specs of the pool are at the end of this entry, but I have an approximately 7200-gallon above-ground Doughboy pool. Sand Filter. Chlorine sanitized. If you need to know how many gallons your pool is, you can look up the formulas, or use an online calculator like the one built in to Pool Math. Also worth noting: I live in southern New England, so any reference to the calendar is dependent on that.

Filtration

We have a sand setup for filtration. The internals can break, but sand filtration is generally easy and efficient. Sand only needs to be replaced maybe every 5-10 years. There are options to improve filtration including adding diatomaceous earth that acts to fill some of the gaps in the sand, increasing the filtration efficiency. There are also sand substitutes/enhancers like cotton-like balls and cellulose fibers, meant to capture junk better. Some chemicals also affect filtration (discussed in the chemical philosophy section)

Pool Pump Speed

When I replaced my original 1 HP Hayward pump, I opted for a variable speed pump capable of 1.5 HP. And for about 2 years, I’ve been using the pump on and off at its maximum speed. At max speed it pushes 80 gallons/min or so. This is too much for my filter, and I’ve learned that it is unnecessary. At slow speed it will push 40 gallons/min. The difference in pool water turnover is that high speed will filter my entire pool in 1.5 hours, low speed wakes 3 hours. But low speed also uses approximately 1/8 the electricity.

You can save money with a variable speed pump by running it on low. Better still, it filters fine particles more effectively on low, as it is less likely to break up clumps and push them through the filter. I didn’t know any of this before today, so now I plan to run my pump almost entirely on low, except for when I’m vacuuming or back-washing.

Filtering With Minimal Electricity

Figure out your pool’s volume (PV) using math, or an online pool volume calculator. Look up how many gallons per minute (GPM) your pump can pump.

Figure out how long (in hours) it takes your pump to force your entire pool through the filter (TT) using this formula.

\[\boxed{TT = \frac{PV}{GPM * 60}}\]

It’s recommended that you pump your pool water completely through the filter once per day. In my case, on high speed, that will take 90 minutes. On low it will take 3 hours. That’s your baseline. On a normal day, don’t run your pump longer than that. If you’ve had a pool party, heavy rainstorm, or some other event that may have gotten organic matter into the pool, increase your time by 50% or even more if something dramatic happened.

It’s likely that this formula is giving you a lower number than you were recommended to run your pump. That’s because people are erring way out on the side of caution and without knowing your pool size or pump rate. Save yourself some electricity, do the math, and pump a little less.

Chemical Philosophy

I have mostly adopted Trouble Free Pool’s philosophy on pool chemistry. That means I use a simple set of generic chemicals, most of which don’t have brand names. They’re entirely sufficient anf this also keeps costs down. ALso, I don’t generally use “algicides.” Chlorine is a sanitizer, and powerful oxidizer, and that’s what kills the algae in my pool.

• Liquid chlorine for sanitizing (12% strength from local sources, but basic supermarket bleach is also effective, though less concentrated, so you’ll need more)
• Baking soda (sodium bicarbonate) to raise pH and Total Alkalinity
• Muratic Acid to lower pH (especially needed if a lot of organic stuff has fallen into he pool)
• Water (it’s a chemical)

I recommend you visit Trouble Free Pool and check out their Pool School. You will learn a lot in a short amount of time, and it could save you a lot of cash. I’ve only paid attention to the recommendations there for chlorinated pools, but they give info on SWG (salt water generator) systems, which essentially maintain a level of chlorine using sodium chloride (table salt).

They helpfully offer a Pool Chemistry Calculator that will tell you exactly how much chemistry to use in your pool. To get accurate measurements of your pool chemistry, you’re going to need a TF test kit. The TF-100 had everything I needed for my above-ground pool. You’ll use the kit for years, and you can get refills when you run out of a reagent. Good testing saves you from wasting money on unnecessary chemicals.

Chemical Exceptions

I think I’ve used a winterizing formula once. I don’t remember what is was. I have used a clarifier, and this is relevant for filtration. I have used two:

• HTH Super Concentrated Clarifier. It’s bright blue, and pretty cheap. You use a tiny bit for my size pool, and dilute it in a bucket first. So it’s not horrible for your pool economy. I have bought the HTH brand, but I believe there are many similar products sold under other brands. They all use a cationic polymer (polyDADMAC). They work through coagulation: the positively charged polymer binds to negatively charged microscopic particles (like dead algae, dust, and organic debris) causing them to clump together so your pool filter can catch them. These do work, and can help if you’re frustrated by a slight haze lingering in your water. I have only ever used this a few times and I’m not sure I ever really needed it.
• Pool First Aid is a name-brand product that combines a polyDADMAC clarifier with some sort of enzyme that can also digest oils. I’m not as familiar with it as I am with other chemicals here; I saw a professional pool maintenance guy use it in an “emergency one-day pool-opening” video, but I keep it on hand as a backup for when all else fails to clear the pool water. In other words, when your levels are all good and the filter has been running, and you know the filter is working, but you can’t get rid of cloudiness. At this point it makes sense to consider you might have an oiliness problem, and you need an enzyme to digest the organic oils. NOTE: if you’re SLAMming the pool, it might defeat the purpose to dump enzymes in there. High chlorine levels probably destroy them. So wait until levels are normal.
• Borates/Borax can help buffer your pool water against fluctuations in pH. Use in conjunction with muriatic acid to fix the pH in place. It can also improve your pool water’s sparkliness and feel. I don’t know a lot about it, and there are reasons not to do it if you have a dog who routinely drinks from the pool. So it’s really unnecessary, but could be considered an exception if you want the benefits of stable pH and “softer” feeling water.

Closing

It’s important to close the pool properly because freezing water can damage almost every part of the system. Here’s a checklist of the most important things to take care of:

• Water completely drained out of the sand filter
• Multiport set to Winter
• Return covered with plastic disc insert under the twist-off collar
• Pump brought indoors
  • Pump hardware (screws) placed in a baggie
• Aquadoor installed to keep water in the pool and out of the skimmer (ice can crack skimmer)
• Skimmer basket brought inside
• Pool cover installed

If pool was properly cleaned and chlorinated late enough in the season, algae doesn’t form over the winter, but it will start to green in April. So even if pool isn’t covered over winter, covering it in late March may keep the water clear. Lazy backup strategy.

Opening

If pool was closed properly, opening is simply a matter of getting the pool cover off (requiring pumping out the water that accumulated) and then attending to the chemicals:

• add chlorine up to maintenance level
• adjust stabilizer (to about 30 ppm)
• Check and fix pH
• Check and fix total alkalinity
• if pool fails OCLT
  • SLAM (shock level and maintain) until it passes an overnight chlorine loss test (OCLT - pass if there’s no or minimal chlorine loss overnight) and the captured chlorine is at or below 0.5 ppm.
• Vacuum or rake or otherwise get rid of detritus
• When pool is clear, swim

In cases where the pool is murky, green, or green-black, SLAM immediately after you get the stabilizer to 30, and pH is in the target range. Once you get rid of the green, the rest of the job is just filtering, as long as the equipment is working properly.

SOURCE: Trouble-Free Pools

Miscellaneous

General above-ground-pool helpful knowledge

Muratic acid 20° Bé (Baumé rating) to bring pH down

It does it very quickly. Great if you’re trying to get the pH down to start killing algae.

Pool First Aid

The product Pool First Aid is a clarifier and some enzymes which are supposed to help break down organic substances and oils. Trouble Free Pools will tell you it’s unnecessary, and it probably is. But it can save you time in cases where you’re unable to get the filter to filter very fine particles fast enough. Other clarifiers probably also do this. Maybe cheaper as well.

Pool Vacuum

The Efurden Cordless Pool Vacuum, Handheld Pool Vacuum came in handy after our sand filter broke and dumped a ton of sand on the floor of the pool.

Pool Hardware Specifications

Equipment Category	Component / Parameter	Exact Model Number / Factory Spec	Crucial Parts & Maintenance Notes
Pool Volume	Total Capacity	7,200 Gallons	Used for calculated chemical dosing and target tracking.
Pump	Brand & Model	Hayward PowerFlo Matrix Dual-Speed	Above-ground specific high-performance series.
	Pump Part Number	W3SP15932S	Use this exact SKU for motor, housing, or lid replacements.
	Horsepower	1.5 HP	Dual-speed motor configuration.
	Physical Dimensions	23.6” L x 9.3” W x 11.6” H	Useful for clearance space checks. Weight: 11.6 lbs.
Filter	Brand & Model	Hayward Pro™ Series High Rate Sand	Depth-filtration tank system.
	Filter Model Number	S180T	Base model designator.
	Exact Model ID	S180T93SFT	Use this code for ordering internal tank parts.
	Unit Serial Number	21120412005878009	Factory tracking ID for warranty or technical support.
	Multiport Valve Model	SP0714T	The Vari-Flo control valve model (needed if replacing the spider gasket).
	Design Flow Rate	34 GPM (128 LPM)	Factory limit. High speed significantly overpowers this; low speed is your safe zone.
	Filter Sand Required	150 lbs (68 kg)	Use #20 Silica Sand, particle size0.45–0.55 mm (.016–.021 in).
	Filtration Area / Max PSI	1.7 sq. ft. /50 PSI Max	Tank structural limit. Normal clean running pressure is 10 PSI.
Skimmer	Brand & Model Line	Doughboy Thru-Wall Skim-Line™ Deluxe	Heavy-duty faceplate wall-mount skimmer assembly.
	Reference Part Numbers	0-2091-013 / 0-2094-013 / 0-2095-013	Look for these base numbers when ordering replacement skimmer baskets or vacuum plates.

Quick-Reference Multiport Valve Cheat Sheet

• FILTER: Default operational setting. Run on Low Speed (40 GPM) for standard daily maintenance and fine particle polishing.
• BACKWASH: Run on High Speed until the sight glass begins to transition from cloudy/milky to translucent (typically 30–45 seconds during heavy clearing).
• RINSE: Mandatory 15-second run after every single backwash. Resets the loose sand bed to prevent a dirty plume from shooting back into the pool. Note: This setting features maximum internal valve friction (head loss).¹

Season Notes

2026

This year was rough for pool opening. I hadn’t closed the pool properly in 2025, and the pool turned black sometime in April after a winter of looking at clear water and thinking “I guess closing is optional.” It’s also possible that careless closing practices caused my skimmer to crack (or it could have been age – likely a combination) and a filter lateral to crack. Something also caused the stand tube to crack. Possibly caused by sand in the tube and pump pressure. I don’t really know.

It took weeks to get the pool clear and open, and I am writing about it here so I don’t have to repeat the experience next year. Close the pool properly, James!

1. The term head loss refers to the friction created in your filtering system. “Head” refers to where the top of a hypothetical column of water ends up if the water is being propelled by your pump. Friction reduces how far the pump can pump the water against gravity, and so you lose height in that column of water. That ‘head loss’ is a proxy measure for the friction in the system past the pump. ↩