Winter Water Level for a Pool With a Deep End and Raised Spa Beam

You drained your pool down last fall, slapped the cover on, and called it done – then spent the following spring staring at a crack running along the raised spa beam that definitely wasn’t there in September. If your pool has both a deep end and a raised spa attached to it, standard winterizing advice mostly doesn’t apply to you, because you’re closing two structurally different vessels at once.

The short answer: drop the main pool water level to 12 to 18 inches below the skimmer opening – never lower, regardless of how deep your deep end goes – and keep the raised spa beam filled to within 6 inches of its top jets or spillway edge. Those two targets are completely independent of each other, and that’s the core of what most pool owners get wrong at closing time. This article walks through why each number exists, how to hit both without draining one into the other, and the order of operations to follow so nothing gets left exposed overnight.

Why a Deep End Changes Your Draining Math

A lot of people think “deep end” means they need to drain further to get the water away from the skimmer. The opposite logic applies. The skimmer is your reference point, not the floor of the pool. Lower the water surface 12 to 18 inches below the mouth of the skimmer and you’re done on the pool side – it doesn’t matter whether your deep end is 6 feet or 9 feet, because there will still be several feet of water covering that floor. That water is an asset in winter, not a liability. It holds weight, stabilizes the shell, and provides thermal mass that buffers the deep end from sharp freezing cycles.

What you absolutely cannot do is drain a pool with a deep end to near-empty. On a fiberglass or vinyl liner pool, hydrostatic groundwater pressure will push the shell upward when there’s nothing inside to counteract it. On a gunite or plaster pool, exposed plaster at the deep end goes through freeze-thaw cycles that cause spalling and cracking. Leaving water in the pool over winter isn’t just acceptable – it’s structurally necessary for virtually every inground pool type.

A worked example: say your pool is a 16×32 with a shallow end of 3.5 feet and a deep end of 8 feet. The total water volume might be around 18,000 to 20,000 gallons. When you drop the surface 14 inches below the skimmer (a safe midpoint in the 12-to-18-inch range), the water column over the deep-end floor is still roughly 6.5 feet deep. That’s a healthy, structure-protecting level. You’re not draining the deep end – you’re just pulling the surface away from the return jets, skimmer, and light niches so freeze-thaw damage can’t reach them.

The Raised Spa Beam: A Completely Different Animal

A raised spa beam is the bond beam – the structural concrete rim – that forms the walls of an elevated attached spa. When people talk about a “raised beam,” they usually mean the spa shell sits several feet above deck level, with the pool below it and a spillway or weir between them. That beam is exposed on all sides to air temperature. Leave it dry in a climate that dips below 32°F and you’re asking for cracked concrete, because water that absorbed into the porous shell earlier in the season will expand as it freezes with no surrounding water to equalize the pressure.

The target: keep the spa water level within 6 inches of the top return jet or spillway lip for winter. Some service techs say as close as 4 inches; 6 inches gives you a safe buffer for precipitation and evaporation over a long winter without putting water over the jets themselves. You want the beam wet and weighted, not brimming.

For detailed guidance on managing an in-ground spa through winter – including equipment winterizing for the spa side – Precision Pool and Spa’s in-ground spa winter guide covers the structural considerations clearly.

Managing Two Water Levels in One System

Here’s the practical challenge: if your pool and spa share a circulation system, draining the pool down to the 12-to-18-inch target can pull water from the spa side through the spillway or connecting plumbing. You need to set the levels independently and in the right order.

1. Shut the diverter valves between pool and spa. Most attached spa systems have a diverter or isolation valve. Close it before you start draining so the two volumes don’t communicate.
2. Set the spa level first. Bring the spa to its 6-inch-below-jets target. If the spa is currently over-full, drain it slightly; if it’s low, top it up. Lock that level in.
3. Drain the pool side to 12 to 18 inches below the skimmer. Use a submersible pump, a waste line, or your filter’s backwash port. Stop checking when the surface clears the skimmer mouth by your target depth.
4. Blow out and plug the lines on the pool side (returns, skimmer, main drain) before temperatures drop. The spa plumbing gets the same treatment: blow out the jets, plug them, and add non-toxic antifreeze if any horizontal runs can trap water.
5. Install expansion plugs in the spa jets after blowing out the lines. These keep winter air and debris out of the plumbing.

One common mistake: people drain the pool first, forget the diverter is open, and watch the spa slowly bleed down through the spillway overnight. By morning the raised beam is sitting with six inches of water instead of a full column, and the exposed upper portion is vulnerable. Check the diverter, then re-check it before you walk away.

What Happens If You Get It Wrong

Getting the pool level wrong in either direction carries real consequences:

• Too high (above the skimmer mouth): Water expands when it freezes. A skimmer with water at or above its mouth can crack the skimmer body as ice forms, a repair that can cost $300 to $600 to fix properly.
• Too low on the pool side: Hydrostatic lift risk on fiberglass and vinyl liner pools, plus plaster exposure damage on gunite pools. A popped liner or lifted shell runs into the thousands.
• Spa beam left low or dry: Freeze-thaw cracking of the bond beam and shell. Beam repairs on a raised spa can cost $800 to $2,500 depending on the extent of the damage and whether rebar is involved.

The proper winter water level is one of those details that feels minor until you’re writing a check in April. It’s also worth coordinating your chemistry before you set these levels – if you’re closing a larger pool and need a reference point for gallon-based chemical dosing, the post on how many gallons an 18×36 inground pool holds is a useful benchmark for doing that math.

Chemistry and Cover Timing

Water level and chemistry are a package deal at closing. Once you’ve hit your target levels on both the pool and spa side, dose both with closing-level chlorine (10 to 12 ppm on the pool side, 5 to 8 ppm on the spa side), adjust pH to 7.2 to 7.4, and bring alkalinity into the 80 to 120 ppm range. AquaDoc’s winter closing kit is a product pool owners use specifically to pre-measure these doses for pool-and-spa combos, which removes one decision from a day that already has too many. Then install the cover within 24 hours so the chlorine doesn’t off-gas before it protects the water through the winter. If you want to get the chemistry side dialed before closing day, fall pool maintenance before you close covers the pre-closing chemical steps in detail.

For the spa side, a solid cover or thermal blanket cut to fit the spa opening helps retain the water temperature longer into fall and slows evaporation over winter – relevant because you need that water level to stay stable for months without topping up. Check the level once a month if you can access the spa under the cover; top up if it’s dropped more than 3 to 4 inches below your starting target.

The winter pool and spa maintenance fundamentals from Ole’s Pool and Spa are worth reading if you want a broader view of what the full closing checklist looks like for a combo system.

Frequently Asked Questions

How much water do you leave in a pool with a deep end for winter?

Leave the water level 12 to 18 inches below the skimmer opening on the shallow end. That number doesn’t change based on how deep your deep end is – you’re setting the surface height, not trying to drain near the floor. The deep end will still have several feet of water covering it, which is exactly what you want.

Should you leave water in a raised spa beam over winter?

Yes, and close to full. Target 6 inches below the spa’s top return jets or spillway lip. Leaving the raised beam exposed and dry in freezing temperatures lets absorbed moisture in the concrete expand as it freezes, which cracks the beam. A column of water inside the spa provides the counterbalancing pressure that protects the structure.

What happens if you drain a pool with a deep end too low in winter?

On fiberglass and vinyl liner pools, draining too low allows groundwater pressure to push the shell upward – sometimes enough to buckle or pop the liner entirely. On plaster pools, the exposed deep-end surface goes through freeze-thaw cycles that cause spalling, delamination, and cracking. Never drain a pool with a deep end below 12 inches under the skimmer.

What water level should a raised spa be at during winter?

About 6 inches below the top return jet or spillway edge. This keeps the bond beam fully wet and structurally protected while still leaving room for minor water expansion. Check it monthly through winter and top up if evaporation or a cover leak drops it more than 3 to 4 inches.

Can you use the same winter water level for the pool and the spa beam?

No. The pool drops to 12 to 18 inches below the skimmer; the spa stays near-full at 6 inches below its jets. They operate as separate vessels with different structural needs. Using the same low level on both is one of the most common winterizing mistakes on pool-spa combo systems, and it’s how raised beams get cracked.

A pool with a deep end and a raised spa beam needs two distinct water levels at closing: 12 to 18 inches below the skimmer on the pool side, and 6 inches below the jets on the spa side. Set them independently, in that order, and both structures will come through winter without the freeze damage that makes spring openings expensive.