The best hydraulic cement for a leak you need to stop now

The only product in this aisle you can use while water is actively coming through the wall. Every basement should own a tub.

Hydraulic cement is a rapid-setting cement that expands slightly as it cures. Both properties exist for one purpose: to let you plug a hole that has water coming out of it. Ordinary mortar washes out before it sets and shrinks as it cures, which is why it fails at this job.

What it is for

• Form tie-rod holes in poured walls — round holes, often weeping, the classic use.
• Pipe and conduit penetrations through the foundation.
• The wall-floor cold joint, where the slab meets the wall — though if water is coming in all along it, the underlying problem is pressure.
• Holes and voids left by removed fixings or broken-out concrete.

What it is not for

• Moving cracks. It is rigid, and it will crack again alongside the repair.
• Structural repair. It plugs; it does not restore the wall's strength.
• Large areas. It is a plug material, not a coating.
• Hydrostatic pressure across a whole wall. No cement applied inside fixes a water table outside.

Quick picks

#	Product	Best for	Score	Price
1	DRYLOK Fast Plug hydraulic cementSets in minutes while wet, expands as it cures, and locks itself into the hole.	Fast setting on an active leak	9.0★★★★★	Check price on Amazon → #ad we earn a commission · Amazon shows the current price
2	Quikrete Hydraulic Water-Stop CementThe same job from the biggest name in bagged cement, usually the easiest to find locally.	Larger repairs and wider availability	8.8★★★★	Check price on Amazon → #ad we earn a commission · Amazon shows the current price

Scores are ours and editorial, not lab measurements — see how we pick. Tap a row for the full write-up.

#1Fast setting on an active leak

DRYLOK Fast Plug hydraulic cement

Sets in minutes while wet, expands as it cures, and locks itself into the hole.

9.0/10★★★★★Our editorial score: 9.0 out of 10

Check price on Amazon →

#ad we earn a commission · Amazon shows the current price

Specifications, as published by DRYLOK (UGL)

Type	Quick-setting hydraulic cement
Set time	3 to 5 minutes
Works under water	Patches holes where water is actively flowing through them
Composition	Sand and cement, 100% solids
Coverage	16 cu in per lb

The chemistry here is genuinely different from ordinary patching compound: it sets fast enough to resist being washed out, and it expands into the void rather than shrinking away from it. That combination is what lets you push it into a hole with water coming through.

Mix no more than a handful at a time. The first time most people use it they mix a bucket and watch two-thirds of it go off before they can place it.

What it gets right

• Designed specifically for stopping running water, not merely tolerating damp
• Expands slightly as it sets, which is what makes the plug hold
• Long shelf life, so a tub bought today is useful in three years

Where it falls short

• Working time measured in minutes — mix tiny batches or waste it
• Rigid: not a fix for a crack that is still moving
• Will not bond to a dusty or unsound surface

Specifications from DRYLOK Fast Plug product data.

#2Larger repairs and wider availability

Quikrete Hydraulic Water-Stop Cement

The same job from the biggest name in bagged cement, usually the easiest to find locally.

8.8/10★★★★★Our editorial score: 8.8 out of 10

Check price on Amazon →

#ad we earn a commission · Amazon shows the current price

Specifications, as published by Quikrete

Type	Fast-setting hydraulic cement for active leaks
Set time	Very fast; mix only what you can place immediately

There is very little to choose between the two on performance. Availability decides it: whichever is on the shelf when you need it is the right one, and this is usually on the shelf.

What it gets right

• Stocked almost everywhere, including at 8pm on a Sunday
• Published technical data to work from
• Economical for larger jobs such as a run of wall-floor joint

Where it falls short

• Same short working time
• Same rigidity limitation
• Larger pack sizes can be wasteful for one hole

Specifications from Amazon listing (search).

Technique: the part that decides whether it holds

1. Step 1Undercut the holeChisel the opening so it is wider inside than at the surface — a dovetail profile. This is the single biggest factor in whether the plug stays put, because it mechanically locks the cement in place.
2. Step 2Clean out dust and loose materialThe cement needs sound concrete to grip. Brush and flush the hole out before mixing anything.
3. Step 3Mix a small batch, stiffEnough for this one hole, mixed to a putty consistency. Too wet and it will not hold its shape against running water.
4. Step 4Press and holdForce it into the hole with a gloved thumb and hold firm pressure for the stated set time, usually a few minutes. Holding is the step people skip.
5. Step 5Let it cure before coatingGive it the full cure time before applying any waterproofing coating over it, or the coating fails along the patch.