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Pond liner fabric Dewitt

Dewitt Protective Pond Underlayment - 4 oz.(12.5' x 360')

SKU PU12.5360
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$1,884.57 - $1,884.57
$1,884.57
$1,884.57 - $1,884.57
$1,884.57
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Dewitt · Pond Underlayment · 4 oz

Dewitt 4 oz protective pond underlayment on a 12.5′ × 360′ roll covering 4,500 square feet. A long roll for larger ponds and waterways where length matters more than width. Non-woven needle-punched fabric that goes in beneath the pond liner, shielding it from sharp objects and supporting it over soft areas.

Weight
4 ozSmooth soil bases
Roll Size
12.5′ × 360′4,500 sq ft per roll
Part Number
PU12.5360Brand: DeWitt
Fabric
Non-wovenNeedle-punched, will not rot
  • Goes beneath the pond liner
  • Tough & puncture resistant
  • Supports the liner over soft areas
  • Permanent — will not rot
  • Free shipping on all orders

01 Goes under the liner · 4 to 8 oz

Dewitt Protective Pond Underlayment

Pond underlay fabric that shields the pond liner from sharp objects and abrasive materials while providing excellent support. It is installed underneath the waterproof pond liner, and it is permanent, tough and designed for a long life span.

The fabric forms a barrier between the liner and anything sharp or abrasive below it — rocks, gravel, ridges — giving a smooth, stable surface that supports the liner rather than letting it bridge over hard points. Designed for man-made ponds, pools and waterways.

3weights · 4 oz, 6 oz and 8 oz

Non-woven, needle-punched fabric in conveniently pre-cut sizes, including two folded to 6′ for easier handling.

02 Why the liner needs it

Water Is Heavier Than It Looks

A liner carries the enormous volume of water sitting above it, and that load concentrates wherever the ground beneath is uneven. Every rock, root and ridge becomes a stress point. Underlayment removes those points by giving the liner a smooth, supported surface to sit on.

03 Worth knowing

Cardboard, Sand And Old Carpet Do Not Work

Plenty of people try to protect a pond liner with whatever is to hand — cardboard, sand, old carpet padding, newspaper. It seems reasonable, and it is the most common reason a pond fails a few seasons in.

Those materials rot away, fall apart or tear. When they go, the liner is left sitting directly on the rocks and ridges the padding was meant to cover, under the full weight of the water — and the repair means draining the pond and lifting the liner. Sand shifts and washes out; carpet holds moisture and breaks down; cardboard and newspaper are gone within a season.

Purpose-made underlayment is a non-woven, needle-punched fabric built to stay where it is put and keep doing the job for the life of the pond. It is the difference between protecting the liner once and protecting it until the padding disintegrates.

04 What you get

Benefits

  • Non-woven, needle-punched fabric
  • Tough and puncture resistant
  • Sturdy, clean and safe material for installation under pond liners
  • Protects waterproof pond liners from sharp objects
  • Provides support over soft areas
  • Conveniently pre-cut sizes
  • Long lasting — permanent, and designed for a long life span
  • Two sizes folded to 6′ for easier handling on smaller ponds
Support over soft areas matters as much as puncture protection. Sharp rock is the obvious threat, but a liner sagging into a soft pocket concentrates load just as badly. The underlayment spans both, which is why it is specified as support as well as protection.

05 Choosing

Which Weight Do I Need?

All three weights are the same non-woven needle-punched fabric. Heavier gives more puncture resistance and more support, and the deciding factor is what is underneath the pond rather than the size of it.

4 ozSeries PU 6 ozSeries PU-6OZ 8 ozSeries PU8
WeightSpecify it when
4 ozThe excavation is reasonably smooth — soil or fine material, no significant rock, ornamental and garden ponds
6 ozSome rock or coarse material in the base, or a larger pond where the water load is greater and you want more margin
8 ozRocky, gravelly or uneven ground, larger or deeper installations, and anywhere the cost of lifting the liner later would be serious
Describe the ground, not the pond. How rocky and how uneven the excavation is decides the weight far more than surface area does. Call (800) 524-4161 and tell us what the base looks like.

06 Roll sizes

Available Rolls

Conveniently pre-cut sizes across the three weights. Two are folded to 6′, which makes a big difference carrying and positioning fabric on a smaller pond.

WeightPart numberRoll sizeSq ft
4 ozPU12100F — folded to 6′12′ × 100′1,200
4 ozPU12.536012.5′ × 360′4,500
4 ozPU1530015′ × 300′4,500
6 ozPU12100F-6OZ — folded to 6′12.5′ × 100′1,250
6 ozPU12.5360-6OZ12.5′ × 360′4,500
6 ozPU15300-6OZ15′ × 300′4,500
8 ozPU8.0-7.53007.5′ × 300′2,250
8 ozPU8.O-1530015′ × 300′4,500
Size it larger than the liner footprint. Underlayment needs to reach up the sides and past the edge of the excavation, and overlaps between runs are not optional — a gap in the underlayment is a gap in the protection.

07 Where it goes

Applications

Garden & ornamental ponds Koi ponds Man-made ponds Swimming ponds & pools Waterways & streams Waterfalls & cascades Retention & irrigation ponds Water features
Anywhere a waterproof liner is being installed over ground that is not perfectly smooth — which is every excavation, once you look at it closely.

08 Installation

Laying Pond Underlayment

The order matters and it only goes one way: excavation, underlayment, liner, water.

Clear the excavation of anything loose and obviously sharp first — underlayment protects against what remains, not against a stone you could have lifted out by hand. Lay the fabric into the excavation, following the contours, and carry it up the sides and past the top edge.

Overlap adjacent runs generously rather than butting them, since the liner will be sitting on the joint. Smooth out wrinkles as you go, then install the waterproof liner directly on top before adding water.

Do not skip the sides. Liners get their worst abrasion where they turn up a bank and where anything rests against them at the edge. Underlayment that stops at the bottom of the excavation leaves the most vulnerable part of the liner unprotected.

09 Free shipping, every order

DeWitt Fabric Shipping

Shipping is free on every order, at any quantity. The map shows standard ground transit times for DeWitt fabric.

Transit times on the map are in business days, are approximate, and are specific to DeWitt fabric only. The day the order ships is not counted as a transit day.

Map of United States ground transit times in business days for DeWitt fabric orders

10 Buying from us

Why Buy Pond Underlayment From Landscape Discount

Genuine DeWitt product

DeWitt is a leader in agricultural and construction fabric in the United States, with over 30 years of product development. We never substitute another brand or fabric without the explicit consent of the customer.

Three weights, eight rolls

4 oz through 8 oz including two folded to 6′, so the fabric suits the ground and the pond rather than suiting what we happen to hold.

Straight answers on weight

Tell us how rocky and how uneven the excavation is and we will tell you which weight covers it. Over-specifying costs money; under-specifying costs a liner.

We answer the phone

When you call you quickly reach a helpful, live person happy to answer your product and order questions. (M-F 5:00 am - 3:00 pm Pacific Time)

11 Common questions

Pond Underlayment FAQs

Does the underlayment go above or below the liner?
Below. The order is excavation, underlayment, waterproof liner, then water. The fabric protects the liner from what is underneath it and supports it over soft spots.
Can I use sand, carpet or cardboard instead?
You can, and it is the most common reason ponds need repairing a few seasons later. Sand shifts and washes out, carpet padding holds moisture and breaks down, cardboard and newspaper are gone within a season. When they fail the liner ends up sitting on the rocks they were covering, under the full weight of the water.
Which weight should I choose?
4 oz where the excavation is reasonably smooth soil with no significant rock. 6 oz where there is some rock or coarse material, or on a larger pond where you want more margin. 8 oz for rocky, gravelly or uneven ground and for larger or deeper installations.
How much do I need?
Size it larger than the liner footprint — the fabric has to follow the contours, run up the sides and reach past the top edge. Add generous overlaps between runs, since the liner will be resting on those joints.
What does “folded to 6 feet” mean?
The roll is folded so it handles at 6 feet wide rather than its full width. On a smaller pond that makes carrying and positioning the fabric considerably easier, particularly working alone.
Do I overlap or butt the seams?
Overlap, generously. A butted joint that opens leaves the liner sitting on bare ground at exactly the point where two pieces of fabric were supposed to protect it.
Do I still need to clear the excavation?
Yes. Underlayment protects against what remains after a reasonable clear-out, not against a rock you could have lifted out by hand. Remove anything loose and obviously sharp first.
Will it rot?
No. It is a non-woven needle-punched fabric, permanent and designed for a long life span, which is exactly what improvised padding materials are not.
Does it need to go up the sides?
Yes, and this is the step most often skipped. Liners take their worst abrasion where they turn up a bank and where anything rests against them at the edge, so underlayment that stops at the bottom leaves the most vulnerable area unprotected.
What does shipping cost?
Nothing. Shipping is free on every order, at any quantity.