my in-laws asked me to do a small repair for an in-ground pool, top suction area.
the pool is a standard gunite diamondbrite finish and the pool cleaner goes into
opening cavity on the very top at water level, into a small round pool where the
suction line exists (another is on the bottom of pool)
in the small round area, there is a small crack in the cement right above the
line or just at the waterline
I have to drain the pool a little but am asking what type of cement to use to
this crack as it will be exposed to the pool chemicals though most of it is
water level. none of this is the actual swimming pool, it's the small round hole
outside the pool wall, about 1 foot away from the wall of the pool and exists
the top suction line into the pool pump
I'm a little confused by the term Hydraulic cement as well
my understanding of it is:
"Hydraulic cement" is a fast setting cement formulated in such a way
that it expands slightly on setting in contrast to common cement which
does the opposite. As such,"hydraulic cement" is used for watertight
patches of small cracks or holes in concrete.
but I don't know if Hydraulic cement can be placed in small quantities
underwater. The concern would be that the water would wash away the
cement or dilute the mix.
I think the main idea of Hydraulic cement is the expansive nature.
"ordinary" concretes made with portland cement can be placed & will
cure underwater as long as care is taken during placement.
A tremie is used so that the concrete is "piped" down through the
water & the concrete exits the tremie into the "blob" of concrete being
placed. Care is taken such that new concrete always enters the "blob"
so that only the concrete on the surface of the "blob" is subjected to
the water / dilution effects.
The end result is quantity of placed concrete underwater where only the
surface concrete has been subjected to the water / dilution effects.
Typically the concrete item is enlarged to take into effect the lose of
concrete quality at the surface.
Not so. Hydraulic cement expands as it sets, sets in the presence of
active water leaks, has about double the strength of ordinary cement
and is waterproof. It would work just fine in the OP's situation.
Your suggestion of a two part epoxy repair would work, as would
polyurethane caulking. It all depends on the size of the crack and how
much he cares what it looks like.
Read the MSDS of the product you cited:
Where the "hydraulic" cement is shown to be ... ordinary portland cement.
Ordinary portland cement is "hydraulic", whatever that means. In civil
engineering it just means "sets by addition of water". But at some point
is came to mean, "meaningless term that gets suckers to pay multiples of
the price for ordinary portland cement". Magic stuff to put in cracks to
stop leaks. It's just ordinary portland cement with an accelerant, folks,
which mixes with water and works in immersion just fine.
Similar makeup, different properties. I'm not sure what you mean by
ordinary Portland cement as there are five different types and numerous
sub-types with different compositions and properties, all called
Portland cement. Hydraulic cement (and no, I don't like the name it is
marketed by any more than you do) expands slightly as it sets to offset
the natural shrinkage. That's the part that makes it effective in
stopping leaks and plugging gaps. Another more accurate name for it is
expansive cement. It is commonly used in bridge construction where
cracks are verbotten. Almost all other cementitious products shrink as
they cure/dry. There is no accelerant in Hydraulic...errr....expansive
cement. Portland cement has additives to retard its natural rapid
setting, most commonly gypsum.
The proper term "hydraulic" has nothing to do with "expansive".
"ASTM C 150 defines portland cement as "hydraulic cement (cement that not
only hardens by reacting with water but also forms a water-resistant
product) ...". That is, all portland cement is hydraulic.
By blending proportions of various aluminates, silicates, and sulfates in
portland cement, the shrinkage/expansion can be controlled. Shrinkage
typically has everything to do with inadequate hydration while curing and
No argument there. We've already agreed that the hydraulic in the name
Hydraulic Cement is a misnomer. Maybe I'll go to the supermarket later
and buy some of that Wet Beer. ;)
Correct. By blending the component materials in Portland cement the
properties can be varied as needed. Hydraulic Cement has the component
materials blended so that it expands slightly as it sets. The bag of
Type I Portland you buy does not expand - it shrinks slightly.
We're agreed that Portland cement comes in different types, that the
properties can be tweaked by adjusting the component materials and that
some cement expands more than others. Why do you feel that they're
selling a bill of goods? They're already making far more money on the
product because it's sold in much smaller quantities for almost the
I used an "underwater" 2 part epoxy putty for this type a repair
It came in two seperate containers (like film containers)
i don't have it any more...stuff dried up after 10 years on the shelf
in the garage
Check your local pool supply
LEAKMASTER Pool Repair Putty
This convenient and versatile epoxy works underwater and cures to a
bright white in 20-60 minutes. One stick format eliminates waste and
PP701 Pool Repair Putty - Hardens in 20-30 minutes to a fiberglass
Yes many epoxies will do service underwater but only some are
formulated for application underwater. Usually moisture will interfere
with the cure of the epoxy.
Other methods of repair will require OP to drawn down the pool level.
With true underwater epoxy OP can do the repair with water in place.
What you are describing sounds like the skimmer niche.
Just use tile grout from Home Depot/Lowes. You can get a small quantity.
Use sanded type if the crack is larger than 1/16", unsanded for thinner
cracks. Variety of colors if you don't need just white.
See my page:
yeah, I read all of that (my eyes are still bleeding)
while I certainly applaud you (and the entire family) for the effort, I wonder
could have written a cliffnotes or 'pool repair for dummies" version? the entire
description on one page is exhausting and one would wish for a summary version
simple "do this but don't do this" type of abbreviated page with appropriate
"click here for the details"
I noted you mentioned the plaster you used (this does not apply to my simple
is not longer made or available for DIY jobs, suppose I went into the plastering
business, what's a homeowner to use these days?
actually, a separate page by itself for "things I have since discovered, ie.
tips, quick notes" would be fantastic.
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