Connect with us

Op Editorials

ASA & ACI Guidelines Are Your Friend

Published

on

Water Dampening - ASA - ACI Guidelines Are Your Friend - Grant Smith

The pictures in this article are ones that I took when I was called out to come look at a pool for remediation of a water loss issue. The homeowner had already contracted to strip it. The pool was demoed 4 weeks before he called me.

The porosity of the shell is evident along with the lack of coverage over the steel. This pool is a perfect example of why you should follow ASA and ACI guidelines. There have been some recent posts about shotcrete application being done incorrectly. There has been some push back about what is the big deal in not insuring that ASA and ACI guidelines are followed.

Just because you don’t have a structural crack does not mean your shotcrete was done correctly. Structural cracks are caused by under engineered pools in bad soil, soil settlement, and lack of rebar in ratio to concrete. Not caring about putting rebound or wall trimmings in the floor, the strength of the air compressor, the application of good nozzle techniques, the PSI of the concrete, keeping track of the concrete coming out of the truck and water curing all contribute to a porous and under strength shell.

Floors and coves need to shot first so rebound and trimmings can be shoveled out. Trimmings and rebound are not shot concrete and letting them fall on top of the floor that you just shot is not an acceptable practice. They need to be shoveled out. The proper PSI as mandated by the ACI for water vessels is 4,000 psi minimum.

There was a discussion on an earlier post about this (in Ask The Masters Facebook group). One person was stressing that it was the water to cement ratio that gave concrete it’s water tightness which is true. But let’s be field practical. Most ready mix plants or dry shotcrete nozzle men cannot get a perfect .45 W/C ratio.

The shotcrete crew will invariably add water while you are in the back supervising the shot. The higher PSI concrete will have less water in it to begin with so that helps keep the W/C in check. Plus the higher psi concrete just has more cement paste in it which also helps with the density of the concrete.

I can easily tell a 2500 psi shell versus a 4500 psi shell. The 2500 psi shell looks extremely sandy and soaks up water like a sponge. My shells are shot with 5,000 psi wet mix shotcrete. the shell is so dense that it actually rejects most of the colloidal silicate that I spray onto it. For the few hundred dollars it costs to raise up the PSI in your shell you are doing your client a favor. And if the client says your shocrete price is higher then educate them on why you the price is higher. Pretty simple. 250CFM air compressors for wet mix and 650CFM for dry mix to insure the density of the concrete.

The great thing about shotcrete is that it slams concrete paste and aggregate together which creates a more dense finished product. If you have ever done cast in place walls or piers you vibrate the concrete to make it more dense and and get out the air pockets and encapsulate the rebar. Shotcrete has the same effect.

Remember the denser the concrete the more water tight it will be. Water curing is essential to keep concrete hydrated while it is curing. By keeping the shell cool and moist it will retain more water that was in the mix to begin with which also help with a denser concrete. It will also help with shrinkage cracks. Shrinkage cracks occur because water evaporates to quickly out of the concrete. Water cure your shells for 2 weeks to a month.

I have seen a lot of engineers lately mandate a 30 day water cure but two weeks should be your minimum. Soaker hoses on a timer are always a good option. Don’t tell or let your client do it. It’s not their responsibility it’s yours!Once again I stress the first layer of water proofing is a proper concrete shell.

Grant Smith

5/5 - (1 vote)

In Memoriam: Grant Smith - featured Op-Editorialist for Pool Magazine and President of Aqua-Link Pools and Spas in Carlsbad, Calif. A former SWD Master, Watershape University faculty member, mentor and instructor; Smith was widely recognized as an expert and thought leader in the swimming pool industry.

Continue Reading
Click to comment


Subscribe
Notify of
0 Comments
Inline Feedbacks
View all comments

Op Editorials

Hair Entanglement in Pools, Are Current Standards Adequate?

Published

on

Hair Entanglement in Pools, Are Current Standards Adequate?

When discussing hair entanglement in the pool and how to prevent these types of incidents from occurring, we have to look at a few things. The first is line velocity. If it is low enough, hair won’t be ingested by the pipe and tangled under the drain lid. Suction entrapment wouldn’t occur either, even if a grate were missing.

Video captured a teen girl nearly drowning after getting her hair caught in the pool.

The second issue pertains to the current codes and standards. Some states have state building codes that dictate maximum line velocities for energy efficiency. California and Florida both mandate line velocities of 6 FPS suction and 8 FPS returns for energy efficiency. 

Current Standards

Residential In-ground Pools NSPI-5/2003 (9.2) the line velocities were limited to 8 FPS suction and 10 FPS returns. (9.2.1) the limit through the drain cover was limited to 1.5 FPS.

Residential In-ground Pools NSPI-5/2013 (9.2) the line velocities were limited to 8 FPS suction and 8 FPS returns. (9.2.1) the limit through the drain cover was deferred to the APSP-7 standard.

Suction Entrapment Avoidance APSP-7 (2013) Piping line velocity is not specified, though the flow rate through the drain cover is limited to 1.5 FPS.

APSP-15 Energy Efficiency Code (2011) 6 FPS suction and 8 FPS return

ISPSC 2015 (311.3) limits the line velocities in the return piping to 8 FPS.  (310) It defers to the specifications in APSP-7 (there is no longer a suction line velocity in the standard).

Suction Outlet Fitting Assemblies APSP-16/2017 (3.9.2) piping line velocities were eliminated, though 1.5 FPS remained as the line velocity through the RDP/SOFA.

RE: Hair Entanglement In The Pool - Decreased distance between the suction pipe and the underside of the drain cover increases the flow through the drain cover.
Decreased distance between the suction pipe and the underside of the drain cover increases the flow through the drain cover.

The safety standards are not addressing energy efficiency. Most experts agree that the optimum efficiencies are achieved at 6 FPS suction and 8 FPS return line velocities. The majority of hydraulic engineers are designing at 4.5 FPS suction and 6 FPS return line velocities. This allows for a margin of error and minor deviations that may occur during construction, while still staying below the maximums. Most codes for public pools recognize the need for low line velocities and therefore limit the velocities at the pipe connected to the main drain to 1.5 – 3 FPS.

The safety standards assume two things occur. The first assumption is that the drain sump size is compliant with the SOFA requirements and the manufacturer’s specifications.  Field-built sumps (divots carved out of the shotcrete) are oftentimes too shallow. Few builders thicken the shotcrete around the suction pipes to allow for a proper depth sump.

The decreased distance between the suction pipe and the underside of the drain cover increases the flow through the drain cover. This increases the danger of hair entanglement, as the design standards and flow rate through the cover have been exceeded. Therefore the sumps are of insufficient size and volume to slow the velocity of the water.

Swimming Pool Expert Witness

Photo Credit: Getty Images

5/5 - (1 vote)
Continue Reading

Swimming Pool Expert Witness - Paolo Benedetti

Utilizing Drainage Mats In Pool Construction

Published

on

Pool Contractor Using Drainage Mat During Pool Construction

Retaining walls, raised pool bond beams and pools with adjacent upslopes all require drainage behind them. But it is impossible to install drainage rock up the walls of a shotcrete pool, without extensive over-excavation, forming and backfilling.

Instead of ignoring these conditions, wise contractors utilize drainage mats installed upon the earth, prior to the placement of the shotcrete. This allows the subterranean water to drain vertically into the drain rock under the pool, where it can be collected and discharged (drained to daylight or via a sump pump).

For high-end projects or all tile vessels, this is critical in reducing negative side water infiltration from the soils. Water passes through the geofabric and into the air gap created by the dimples in the plastic sheet. The drainage mats are available with dimples of various sizes to match the anticipated water flow.

Drainage mats can also be used horizontally between coffers and vessels to assist in the lateral discharge of water. The drainage mats can be nailed to the soil prior to steel placement or utilized in place of steel-tex.

Photo Credits: Carlisle Coatings & Waterproofing Systems

Swimming Pool Expert Witness

5/5 - (1 vote)
Continue Reading

Swimming Pool Expert Witness - Paolo Benedetti

Indoor Pools & Water Vapor, What You Need To Know

Published

on

Indoor Pools & Water Vapor, What You Need To Know

Indoor pools are very unique. The water vapor escaping from the pool is trapped in the building envelope. These vapors are potentially corrosive, as they contain chlorine, chloramines, or ozone. The water can have destructive consequences and pose serious health issues if the building is constructed incorrectly.

Dehumidification of indoor pools is absolutely essential in order to avoid costly damage and repair work.
Dehumidification of indoor pools is absolutely essential in order to avoid costly damage and repair work.

Dehumidification for Indoor Pools

There is no such thing as an oversized dehumidification system. But the lack of a dehumidifier (or an undersized one) allows the water vapor to accumulate and penetrate the building envelope. Water vapor inside the walls can cause corrosion of the structural beams, braces, and brackets, corrosion of the wiring and electrical components, foster mold and algae growth, rusting of HVAC ducts, or promote dry rot of wooden elements. Excess water vapor in the building can lead to a series of air-borne health maladies or bacterial infections.

Indoor pool mold from excess water vapor.
Indoor pool mold from excess water vapor.

Been There, Done That

Cheap clients who do not want to pay for the installation or operation of a dehumidification system, think that they can reinvent the wheel with exhaust fans, sliding doors, skylights, ceiling fans, or other schemes. Trust us, they have been tried countless times without success.

Proper Building Envelope for Indoor Pools

It is important to install a vapor barrier and use moisture-resistant construction materials to prevent the migration of moisture into the walls and ceiling. Electrical outlets, fixtures, and penetrations must be sealed against vapor intrusion.

Without Vapor Barrier vs With Vapor Barrier - Indoor Pools
Indoor Pools – Without Vapor Barrier VS With Vapor Barrier – Photo Credit: Aquatic Mechanical Design

Air Pressure in Indoor Pools

The air pressure within the swimming pool enclosure must be less than the adjacent spaces. Maintaining a high pressure in the adjacent spaces ensures that the water vapor does not migrate.

Operational Cost

Operating a dehumidification and air handling system to control the air pressures, temperatures and humidity are expensive to operate. Failure to operate these systems properly will result in vapor migration and degradation of the building. Maintaining the proper temperatures is also important in controlling the creation of water vapor (evaporation).

Automatic Pool Cover

Using a pool cover does not eliminate the need for a dehumidification system. It will help reduce the vapors, but it will not eliminate them. The installation of a cover allows for the reduction in the size of the dehumidification system, as the loads are reduced.

Qualified Indoor Air Quality Expert

We do not profess to be experts in this field. Though we have built a number of indoor pools, we rely upon specialists in this field. Most mechanical engineers or dehumidifier manufacturers do not possess the skills to properly design the HVAC/Dehumidification system, vapor barriers, building envelope, ducting sizes, or air handling register/return locations.

Non-Corrosive Air Ducts

Properly constructed indoor pool air handling systems utilize non-corrosive plastic ducting, registers, and returns. Galvanized sheet metal ducting quickly begins to corrode in an indoor pool environment. Indoor pools can be a source for year-round enjoyment of a pool. But they require a properly designed and built enclosure, in order to protect the rest of the building and occupants’ health.

Swimming Pool Expert Witness

5/5 - (12 votes)
Continue Reading
Follow us on Google News

Pool Service Software

Pool Service SoftwareSponsored Advertisement
New Orleans Pool Builders - Baton Rouge Pool BuildersSponsored Advertisement
Sponsored Advertisement
CPO School - Space Coast Pool SchoolSponsored Advertisement
Sponsored Advertisement
Sponsored Advertisement
Become a Member of the Pool & Hot Tub AllianceSponsored Advertisement
Houston Pool Builders - Beyond Blue PoolsSponsored Advertisement
Houston Home Theaters - Outdoor Sound SystemsSponsored Advertisement
Sponsored Advertisement
Pool Magazine App on Google PlayPool Magazine App on Apple Store

Download the NEW Pool Magazine App

Recent Pool News

Advertisement
We Build Professionals - Genesis - The World Has Changed, And So Have We.

Pool Monitoring Device

Pool Monitoring Device
Become a Member of the Pool & Hot Tub Alliance

Pool News

Subscribe to Pool Magazine. Join our mailing list.
Subscribe to Pool Magazine on Google News and Join our Mailing list to receive pool news right in your inbox!
Subscribe to Pool Magazine
Pool News & Features
* indicates required
* indicates required
Subscribe to Pool Magazine
0
Would love your thoughts, please comment.x
()
x