Closing a pool in New Hampshire isn t just about tossing on a cover and hoping for the best. Our freeze-thaw cycles, heavy fall leaf drop, and long winters can turn small end-of-season mistakes into cracked plumbing, stained surfaces, algae blooms under the cover, and an expensive spring reopening.
In this guide, we walk through a practical, homeowner-friendly pool winterization process we use across New England. If you want us to handle the closing for you (or repair damage from a past closing), call 888-611-7665 or request an estimate.
When should you close your pool in New Hampshire?
For most outdoor pools in the Granite State, we recommend closing when water temperatures stay consistently around 60 F or below. Closing too early can trap warm water under the cover and encourage algae. Closing too late increases the odds of a hard freeze before plumbing is protected.
- Target water temp: ~60 F and trending down
- Plan for at least 1 weeks of clear weather to finish prep
- If you re in higher-elevation towns, close a bit earlier than coastal areas
Quick recap:
- Close based on water temperature, not the calendar
- Avoid closing while water is still warm
- Don t wait until the first freeze warning
Winterization checklist overview (the order matters)
Winterizing is a sequence. Chemistry first, then cleaning, then water level, then equipment, then plumbing, then cover. Skipping around is how we see missed steps.
- Balance chemistry and add closing chemicals
- Deep clean: brush, vacuum, skim, and clean baskets
- Lower water level to the correct height for your cover type
- Shut down equipment safely (pump, filter, heater, salt system)
- Blow out and plug lines (or use antifreeze where appropriate)
- Install and secure the cover
Quick recap:
- Do chemistry and cleaning before you touch water level or plumbing
- Protect equipment and lines before the cover goes on
- Finish with a tight, secure cover installation
Step 1: Balance water chemistry before closing
Water balance protects surfaces and equipment during the off-season. If your pool is plaster, quartz, or pebble, balanced chemistry is even more important to reduce etching and scaling.
What to test and adjust
- pH: Aim for 7.4
- Total alkalinity: Typically 80 ppm (varies by pool type and sanitizer)
- Calcium hardness: Keep in range for your finish to prevent corrosion or scaling
- Free chlorine: Bring to the high end of normal before closing
- Cyanuric acid (stabilizer): Don t let it creep too high going into winter
If you re using chemicals, handle and store them safely. The CDC has a useful overview (CDC pool chemical safety).
Quick recap:
- Test and balance before adding winterizing products
- Balanced water reduces stains, scale, and surface damage
- Follow safety guidance when handling chemicals
Step 2: Deep clean so you re not closing on debris
Anything left in the pool becomes a stain or algae food source. In New Hampshire, leaf tannins are a common cause of brown staining under covers.
- Skim and vacuum thoroughly
- Brush walls, steps, and the waterline
- Empty skimmer and pump baskets
- Clean the waterline tile (especially if you have a visible ring)
If your tile or grout is damaged, it s better to address it before winter. See our guide to pool tile repair in New Hampshire.
Quick recap:
- Clean aggressively before closing to prevent stains
- Leaf debris and organics drive winter algae problems
- Fix failing tile/grout before freeze-thaw makes it worse
Step 3: Lower the water level (but don t overdo it)
How far you lower water depends on your cover system and your pool s plumbing configuration. The goal is to protect the skimmer and prevent water from reaching returns once lines are winterized.
Common guidance we use
- Mesh safety cover: Often 12 inches below the skimmer opening
- Solid safety cover: Similar or slightly lower to allow room for rain/snow melt management
Lowering too much can expose plaster and accelerate winter surface damage, especially if the pool is uncovered for a few cold nights during the process.
Quick recap:
- Lower water enough to protect skimmer/returns
- Avoid draining excessively (surface risk)
- Match water level to cover type and line layout
Step 4: Shut down and drain equipment correctly
Pool equipment holds water in housings, filters, and heaters. If that water freezes, it expands and can crack expensive parts.
Pump, filter, and heater winterization basics
- Turn off power at the breaker (not just the timer)
- Remove drain plugs and let water fully drain
- Open air relief valves on filters
- For heaters, follow the manufacturer s winterization steps and ensure the heat exchanger drains
If your pool has a salt system, remove the cell and store it indoors if the manufacturer recommends it. If you re planning a larger upgrade, our pool renovation timeline article explains how equipment work fits into a renovation schedule.
Quick recap:
- Kill power at the breaker
- Drain all housings and open valves so nothing traps water
- Don t forget heaters and salt cells
Step 5: Blow out and protect plumbing lines (the most important step)
In New England, plumbing freeze damage is one of the most expensive small mistake issues we repair in spring. The safest approach is to blow out lines with the right equipment and plug them properly.
Which lines need attention
- Skimmer line(s)
- Main drain (depends on configuration)
- Return lines
- Cleaner lines / water features
Antifreeze: when it helps and when it doesn t
Pool antifreeze can be useful in specific situations, but it s not a substitute for properly clearing lines. If lines aren t cleared, antifreeze can dilute and still freeze in low points.
If you re worried you may have an existing leak, solve that before winter. Here s our guide on how to tell if your pool is leaking or just evaporating.
Quick recap:
- Plumbing protection is the #1 priority in New Hampshire closings
- Blow out and plug lines; don t rely on antifreeze alone
- Address suspected leaks before you winterize
Step 6: Choose the right cover and install it tightly
Your cover is your winter roof. A loose cover lets debris and sunlight in (algae), and it can allow ice to push and rub against coping and tile.
Safety cover vs tarp covers
- Safety covers: Cleaner, safer, and generally better long-term protection
- Tarp/water bag covers: Lower upfront cost but more maintenance and risk of mid-winter issues
The Pool & Hot Tub Alliance shares general closing guidance (Pool & Hot Tub Alliance pool closing guidance).
If your coping is cracked or loose, cover tension and winter ice movement can make it worse. See our pool coping repair cost guide for what to expect.
Quick recap:
- Install the cover tight and secure
- Safety covers reduce mid-winter maintenance and safety risks
- Weak coping/tile can be stressed by winter movement
Common New Hampshire winter pool problems (and how to prevent them)
1) Green water in spring
Usually caused by closing too early (warm water), poor sanitation at closing, or a cover that lets light and debris in.
2) Cracked lines or fittings
Most often from incomplete blowout or trapped water in low points. This can mean major repairs in spring.
3) Surface staining and scale
Organic debris and unbalanced water can lead to stains. Hard water scaling can form if chemistry is off.
4) Deck and coping damage
Freeze-thaw can heave deck sections and loosen coping. If you re concerned about traction or coating wear, read about slip-resistant pool deck coatings.
Quick recap:
- Most spring problems trace back to water balance, debris, or plumbing winterization
- Freeze-thaw can affect decks and coping around the pool
- Preventive work in fall is cheaper than repairs in spring
FAQ: Pool closing and winterization in New Hampshire
Do we need to winterize if we have a safety cover?
Yes. The cover helps protect the pool, but it doesn t protect plumbing and equipment from freezing. Proper winterization is still required.
Can we close our pool ourselves without a compressor?
You can handle a lot of the prep yourself (chemistry, cleaning, lowering water), but blowing out lines correctly typically requires dedicated equipment and experience to avoid damage.
Should we drain the pool completely for winter?
In most cases, no. Fully draining can risk structural issues and can expose surfaces to harsh winter conditions. It s usually better to lower to the recommended level and winterize lines.
What if we already had winter damage last year?
If you ve had cracked lines, broken fittings, or recurring spring leaks, we recommend an inspection and repair plan before closing. See our article on winter pool damage repair costs, then call us to schedule service.
Need help closing your pool in New Hampshire?
We close and winterize pools across New England, and we also repair the common damage caused by improper winterization. Call 888-611-7665 or request an estimate and we ll take it from there.
If you re planning for spring, keep our New Hampshire pool opening checklist handy so you re ready when the weather turns.