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Rowa pressure sensitive water pump used for water pressure boosting or rainwater harvesting (C) Daniel FriedmanVFD Variable Frequency Drive Pumps
Constant Pressure Water Pumps
Control omits pressure tank & delivers water to meet varying needs

  • POST a QUESTION or COMMENT about pressure sensitive water pumps for rainwater harvesting or water pressure boosting; using an inline pump controller, omitting a water pressure tank.

Constant pressure or pressure-sensitive water pump systems & inline water pump controllers are explained here where we define and list the common applications of and advantages of VFD water pumps.

This article explains how pressure sensitive pumps and inline pump controllers provide water pressure boosting, rainwater harvesting, or similar functions without requiring a water pressure tank. We explain pressure sensitive pumps and for similar as well as for higher water volume or pressure applications we describe inline pump controls, how they work and where are they most often used.

Our page top photo shows a model set-up for a Rowa brand pressure sensitive pump and control system suitable for water pressure boosting, cistern or rooftop water storage tank water delivery, or rainwater harvesting systems. This system can operate without requiring a separate hydropneumatic or water pressure tank.

InspectAPedia tolerates no conflicts of interest. We have no relationship with advertisers, products, or services discussed at this website.

- Daniel Friedman, Publisher/Editor/Author - See WHO ARE WE?

VFD, Pressure Sensitive Water Pumps

Water pump control that avoids needing a pressure tank (C) Daniel Friedman] Pressure sensitive or "constant pressure" water pumps and inline VFD (Variable Frequency Drive) pump controllers can provide water pressure boosting, rainwater harvesting, or similar functions without requiring a water pressure tank.

What are pressure sensitive pumps and what are inline pump controls, how do they work and where are they most often used?

At WATER PUMP TYPES we explain that

VFDs constant-pressure or variable frequency drive pumps maintain constant water pressure on its output side by varying the motor speed or rpm according to the demand. A check-valve on the pump's output side prevents back-flow from the pressurized side of the pump when the pump stops.

Manufacturers of VFD pumps such as Grundfos and DAB produce variable frequency drive pumps, also known as constant-pressure pumps, that use a motor controller to vary pump speed and thus output in order to maintain a constant pressure in the water system, increasing pump speed as water usage rate increase, and vice versa.

Article Contents

Applications & Benefits of VFD Constant Pressure Pumps & Motors

There is a wide range of applications in which VFD pumps are most-suitable, particularly where variable torque is useful such as in centrifugal pumps used in handling wastewater or in supplying varying needs of potable water.

Really? Well in opinion, yes, the above applications and our own use experience with VFD pumps provides ample and economical justification for their use.

But we were stunned to find, in researching this topic, that Cycle Stop Valves, a company producing a device intended to protect pumps from damage from short-cycling, has written what is in our view a highly-opinionated, self-serving Cyclestop article [PDF] claiming that VFD pumps are unnecessary, a scam, and supported by lies and false claims.

It's fair to say that not all plumbers are fans of VFD pumps and some dislike specific brands and models that in their experience were troublesome. However we should not confuse opinion with more-reliable unbiased research.

Our review of that Cyclestop Valve article found it to be factually incorrect. Which in our OPINION is too bad since other than shooting themselves in their own foot by those claims, Cycle Stop valves are a perfectly-legitimate, functional product.

We're disappointed in Cycle Stop whose product we've described in detail

at WATER PUMP SHORT CYCLE STOP VALVE

Watch out: a cycle stop valve is not a proper repair for a well pump that is short cycling - turning on and off rapidly, perhaps every few seconds or four or more times a minute when water is being run. If your well pump is cycling rapidly in that manner, before installing a cycle stop valve, check for a water-logged pressure tank.

Some Pressure Sensitive Water Pumps Omit Water Pressure Tank

Water pressure booster pumps including models that omit the need for a separate water pressure tank are used as building water pressure boosting systems, irrigation system water pressure improvements, agricultural and horticultural applications, and in industrial processes requiring a constant water pressure and flow rate.

Other VFD and pressure booster pumps are designed to work with a small pressure tank (municipal water pressure boosting) or a much larger one (well water systems).

Water pressure booster pump without water tank at Amazon

Above is the Simer Water Pressure Booster pump illustrated by the manufacturer.

Water pressure booster pump without water tank at Amazon

Shown above are two water pressure booster pumps that use a pressure-sensitive control and omit the requirement for a water pressure tank

. At above left is a 1 1/2 horsepower pressure booster pump suitable for a whole-house water system pressure boost, while at right in that illustration is the Simer 3/4 HP inline "on demand" pressure booster pump.

Grundfos SCALA2 pressure pump being installed at a home in San Miguel de Allende, Guanajuato (C) Daniel Friedman

Shown above: a Grundfos SCALA2 (aka ScalaII or Scala II or Scala-II) tankless water pressrue pump in process of being installed atop a home in San Miguel de Allende, Mexico in March 2017.

Scala 2 pump leak + rubber pad mount details (C) InspectApedia.com

Though the pump is very quiet we also mounted it on rubber pads (white arrow) to reduce noise transmission through the concrete roof that also forms the ceiling of an office located immediately-below.

I'm still a fan of this sophisticated pump, though by December 2018 this unit had a main seal leak (yellow arrow) about 20 months after original installation (March 2017).

See its performance discussed at

Other VFD pumps and their suppliers are given below on this page.


Water Pressure Booster Pump Installation Notes & Warnings

Generally your pump should be installed in a dry area, protected from the weather and from freezing. Some units like the Scala 2 are also rated for outdoor use.

Check the pump manufacturer's installation instructions for the proper location of check valves in the piping system. Some pressure boosting pump models include a built-in check valve while others require an external valve or if pumping from a well, a foot valve.

Watch out: Check the pump manufacturer's advice about the maximum allowable input water pressure. If you are using the pump to boost building water pressure, for safety you may be required to install a pressure reducer/regulator on the municipal water supply line to limit the water pressure into the pump to a maximum of 20 psi (or other pressure specified by the pump manufacturer.

Watch out: warnings in the installation instructions for some of the pressure booster pumps we examined advise that you should never allow the pump to run "dry" as the pump will be damaged.

The pump body and suction line must be filled with water before the pump is turned on.

Watch out: sand and debris, such as from water obtained from a driven point well can damage the pump.

If there is sand, sediment or debris in the water supply protect the pump with an appropriate filter on the suction side of the pump.

Watch out: for leaks in the plumbing system that can damage the booster pump or that may show up in response to new, higher water pressure levels in the building or due to banging pipes that may occur due to increased water velocity when the tankless water pressure booster pump is installed.

VFD Water Pump Pressure Tank Settings

Gould's Goulds 13159RB115, ResiBoost Series, BOOSTER SYSTEM with TANK for Municipal water pressure boosting - cited & discussed at InspectApedia.com

On constant pressure or VFD water pump systems, some designs use a pressure tank, either a small 2-gallon tank or a larger one.

The small pressure tank smooths out the VFD pump's water deliver at low flow rates and in the factory or default 2-gallon size, is used when the VFD pump system is functioning in an individual home or building as a pressure booster for a municipal water supply system.

Where a VFD pump system is used with a large water storage tank as a re-pressurizing system or with well water supply, often a larger water pressure tank will be installed as well, configured as shown below.

Gould's Goulds 13159RB115, ResiBoost Series, BOOSTER SYSTEM with TANK for repressurizing water - cited & discussed at InspectApedia.com

Our examples here make use of Gould's Goulds 13159RB115, ResiBoost Series, BOOSTER SYSTEM with TANK for which the IO manual is given from Xylem below on this page.

On 2023-05-08 by Larry Grotenhuis - what's the correct pressure tank setting for use with a VFD water pump / controller?

what pressure should I set my expansion tank bladder at on a Constant Pressure Well System? My VFD is set at 60 PSI on the controller.

I have a 2 gallon Well-X-Trol expansion tank.

This Q&A were posted originally

at WATER TANK PRESSURE SELF-INCREASE

On 2023-05-08 by InspectApedia Editor (mod) - pressure tank is set to 20 psi below the VFD pump pressure setpoint

@Larry Grotenhuis,

Thanks, that's a really helpful constant pressure pump + pressure tank settings question.

Why is there a little pressure tank at all on a VFD constant pressure water pump system?

The answer is that at very low flow rates, such as a single toilet flush tank re-filling, the pressure tank can let the VFD pump rest - at use rates that are so low that they're below the low-end of the pump's intended/expected delivery rate.

This is avoiding what can be more of a problem than one might think. For example, at the variable flow Scala 2 pump we use for lots of examples in this article series,

see
https://inspectapedia.com/water/Water_Pump_Pressure_Sensitive.php VARIABLE FREQUENCY / VARIABLE SPEED DRIVE WELL PUMPS (VFDs)

we found that when the water softener system is running in regeneration mode the flow rate can be so long and so slow that the VFD pump thinks that there is a water leak somewhere. That can cause the VFD pump's protection circuit to actually shut the pump off entirely, fouling up the softener's regeneration process.

What is the proper pressure tank setting for a VFD water pump system?

- an example answer, using the Xylem Goulds 13159RB115, ResiBoost Series, Booster System with Tank IO MANUAL

the company says

Set the air pressure (pre-charge) in the tank with the tank empty of water.

Pre-charge must be adjusted to be 20 psi below the Pressure Setpoint (SP) based on 5 psi pressure drop.

Notice that this is significantly-different than the "2 psi below pressure switch cut-in" for conventional pump and tank systems.

So you set the required operating pressure of your water system (that's the SP given above) using the pump's set-up instructions, then set the tank pre-charge as we just indicated, to 20 psi below the setpoint.

I think that for your system running at 60 psi that means your little 2 gallon expansion tank air pre-charge, set with the system EMPTY of water and pressure - would be set to

40 psi.

Thanks for really helpful question, let me know what you think.

- the "right" answer depends on the brand and model of VFD pump and tank that you have installed, so please give us that information so that together we can see what the IO manual wants us to do

Pressure sensitive water pump sources & IO Manuals

Pacific Hydrostar water pressure booster pump - at Harbor Freight Tools harborfreight.com

InspectAPedia is an independent publisher of building, environmental, and forensic inspection, diagnosis, and repair information provided free to the public - we have no business nor financial connection with any manufacturer or service provider discussed at our website. We do not sell products nor services.

Pressure Sensitive Pump & VFD Variable Frequency Drive Pumps Research

Rowa pressure sensitive water pump system omits the water pressure tank (C) Daniel FriedmanA look at some relevant patents, books and other documents can help us understand how pressure sensitive water pump controls work.

...


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Reader Comments, Questions & Answers About The Article Above

Below you will find questions and answers previously posted on this page at its page bottom reader comment box.

Reader Q&A - also see RECOMMENDED ARTICLES & FAQs

On 2020-01-21 by (mod) - what is the cut-in pressure for a VFD pump? Performance curve for VFD or Variable Output Pumps like the Scala2

VFD pump curve Forgive me anon I"m not sure what's meant by "running through VFD"

I make "VFD" pumps to be a variable frequency drive centrifugal pump.

There are two similar approaches: an external control box that operates the pump (or another machine) providing variable speed control by varying the electrical frequency (VFD) or a VFD pump that includes that control built into the pump assembly itself.

Those pumps have (at least mine, a Scala-2 does) their own pressure sensor and on-pump settings that allow the user to select levels of delivery pressure or flow; then the pump will speed up to keep up as more fixtures are opened in the building.

The pump's rated cut-in and maximum rates are given in the pump specs, but that's not going to be a fixed set of numbers, rather it's ar range.

You can of course put a pressure gauge on the system and monitor line pressure as water is being used to see the dynamic pressure. Static pressure won't mean a thing.

I describe this type of VFD pump

at WATER PUMP VARIABLE FREQUENCY / VARIABLE SPEED DRIVE (VFDs) [web article] - pressure-sensitive, tankless water or "mini-tank" pressure booster pumps

Operating instructions and performance details & specifications for the Scala II variable speed (variable output pressure & flow) are

at Grundfos Scala 2 PUMP MANUALS [Web article]

About the pump running continuously, that sounds as if you have one of the following problems:

Check this first: debris clogging the non-return valve or check-valve on the pump outlet

there's a loss of water supply and the pump can't reach its (low) internal shutoff

there's a leak somewhere

the pump's pressure sensor is debris clogged or has failed

there is a failed control

More things to check in general (not specific to your pump type) are found by using the on page search box for

WATER PUMP WON'T STOP RUNNING

On 2020-01-20 by Abdul Rehman

How can we know about the cutt-in pressure of booster pump that is running through VFD.

My booster pump is controlling through hydrovar VFC. It is running continuously. Their is no water leakage, NRV is ok.

No leakage in pressure vessel. It's cutt-off pressure is 2.5 bar but I don't know about cutt-in pressure.

This Q&A were posted originally

at WATER PUMP INTERMITTENT CYCLING

On 2018-10-30 by (mod) - why does the constant pressure pump cycle on and off rapidly?

Little Giant CP constant pressure pump described at InspectApedia.comBrett

re your question about why during demand, your water pressure pump cycles on for 3-4 seconds and stops for 3-4 seconds,

That sounds as if you may be missing a pressure tank - on the system or there could be an obstruction in the outlet piping.

Here is what the pump manual tells us:

The Inline System needs a small pressure tank placed on the pump outlet to maintain constant pressure.

The tank supplies water while the pump ramps up to speed and in circumstances where only a small amount of water is required for a short period of time. In addition, the tank prevents water hammer by acting as a system buffer.

This buffer also helps to prevent pressure spikes when there is a sudden change in demand. For 12 gpm (45 lpm) flow or greater, minimum pressure tank size is 4 gallons (15 L); for 12 gpm (45 lpm) flow, minimum pressure tank size is 2 gallons (7.5 L).

Pressure Tank Pre-charge (PSI) The pressure tank pre-charge setting should be 70% of the system pressure sensor setting as indicated in the preceeding table. - see the IO Manual table on page 3.

If you don't have the IO manual for your pump you can obtain one from

On 2018-10-30 by Brett

Brett said:
Thank you for responding... I don't see the reply I posted earlier today so will try again...

I have the Little Giant In-Line CP, Model # 25LGIL1100N4.

- link deleted by moderator, see image above.

Little Giant pumps (Franklin Electric) website is littlegiant.com -

With that info, it's pretty easy to find the install diagram. Plumber's design matched the diagram pretty closely. He added a bypass to be able to go back to a non-pump-assisted flow.

First, thank you for the reply. I appreciate your time and willingness to help.
The pump is a Little Giant CP. http://littlegiant.com/products/water-systems/constant-pressureboosting-systems/inline-cp/
Model # : 25LGIL1100N4

Above is a picture of the Install instructions which the plumber followed pretty well from what I can tell...
<<i'm having trouble getting a menu to appear after choosing "add image" >>

...but you can find the installation PDF pretty easily by Googling "little giant constant pressure" and looking for the PDF, "Constant Pressure System -- Little Giant Pump"

These questions were posted originally at WATER PRESSURE BOOSTER PUMP - the home page for this topic. You will want to check the advice given there.

On 2018-10-29 by (mod) - review the pump manufacturer's instructions about pressure tanks, pressure settings, pump cycling con trols

Brett

Let's start with a careful review of the specific pump brand and model and thence its installation instructions.

If you installed a pump that is designed specifically to work *without* a pressure tank, and as you have a pressure tank installed, that could be causing the trouble you describe.

On 2018-10-29 by Brett - constant pressure inline water pump cycling issue

I had a constant pressure inline water pump professionally installed in the basement of my single story home. Incoming pressure is around 30psi; the pump is set-up to supply the outgoing water to the house around 60psi. During demand, the pump cycles on for 3-4 seconds and stops for 3-4 seconds, etc.

When the pump stops, a single 'clunk/thud' type noise can be heard behind the basement wall where the water pipe enters the house.

Currently the water pressure TANK shows 54psi. I recall my plumber telling the tank should be around 42psi (+/- 2).

Question is: could the noise I'm hearing be caused by the pressure tank having too high pressure?

Also worth noting, the demand from my irrigation system has the pump running steady for the duration of an irrigation zone -- the pressure maintains a constant 60psi. But there is no 'clunk/thud' when the system cycles to the next zone.

 

Reader Question: I got rid of my pressure tank and now am having trouble with short cycling.

(July 5, 2015) Mike Lambadarios said:
Have had problems with water supply ended up doing away with the header tank and pressurised the system directly to the house.

Ran fine for quite a while but is now constantly short cycling,I removed the bladder tank and blocked off the fitting again ran fine for a while but now back to short cycling again.

Was it a mistake to pressurise directly to the house and should I reinstate the header tank?

Reply: either install a water pressure tank (header tank) or install a pressure-sensitive water pump system.

MIke

Pressure-sensitive water pumps

You need either a pressure tank installed to prevent short cycling of the pump, or you need a special hydropneumatic pump control that combines the pump with a pressure switch - shown at left. This is essentially is a switch that can turn a pump on and off when needed without short cycling.

Scala 2 pressure control and leak indicator (C) Daniel Friedman at InspectApedia.comWhile there is a variety of tankless pressure boosting water pumps available, typically an electronic control built into or attached directly to the pump senses either a pressure drop or the flow of water when a faucet or fixture is opened in the building. The control turns on the pump and in addition the controller maintains constant water pressure until the fixture is closed.

The pump will then stop after a brief interval of a few seconds.

A tiny built-in or attached pressure tank is factory pressurized at the "cut-in" pressure for the pump and forms part of the control that prevents rapid on-off pump short cycling.

For details about the Scala2 pressure sensitive booster pump see details

at GRUNDFOS SCALA 2 PUMP GUIDE

For short cycling pump diagnosis and repair

see WATER PUMP SHORT CYCLING.

Water pressure booster pumps are widely used with rooftop water tank systems, in buildings where municipal water supply pressure is low, on shallow well systems and driven point wells, in irrigation systems and in similar applications.

Both tankless designs using an electronic pressure sensor and flow sensor and perhaps a tiny built-in pressure tank, and pressure booster systems designed to work with a separate water pressure tank (Amtrol) are available and are listed later in this article.

Pressure booster pump models, including the Walrus TQ series, include controls specifically designed to prevent the pump motor from cycling on and off (short cycling) when water is being run, enhancing the pump's ability to deliver water at a constant pressure.

The pressure operating range varies by pump design, brand, and model but pump pressure boost capacities are typically between 30 and 75 psi (supporting a water piping height of up to 170 feet) and deliver water at flow rates ranging from 17 to 70 gallons per minute depending on variables such as incoming pressure, pipe diameter, piping length and rise, etc.

Grundfos-VFD-Scala-2 installed in Guanajuato (C) Daniel Friedman @ InspectApedia.com

In our photo at above left that silver domed gadget above the red pressure-sensitive water pump works with the silver micro-pressure tank to provide a boost to water delivered (typically) from a rooftop water tank. No water pressure tank is used with this system.

These systems are typically used as water pressure boosters and not as the primary water source pump. The little silver dome dome is a miniature pressure tank itself, pre-charged to 7 psi and the whole system is calibrated to avoid short cycling of the water pump.

Pre-charged pressure control on a pressure-sensitive water pump (C) Daniel Friedman Mexico This equipment is distributed by bombasrowa.com and is widely distributed in Mexico where often we want simply to boost the pressure delivered by a rooftop water storage tank. Keep in mind that the total flow rate and building water service from this sort of system is of limited capacity.

Often we see pressure sensitive water pumps or inline pump controllers used with rainwater harvesting systems and cisterns or rooftop water tank systems serving small buildings. Submersible models of these pumps are also available for installation in the water tank.

Similar devices are sold by Aqua Group in India: the Aquatex APS hydropneumatic system. This approach floats a very small internal-bladder type pressure tank atop the water pump. Other models are used in marine applications such as the Shurflo and the Jabsco.

Typically a check valve is also required with pressure-controlled water pressure booster or rainwater harvesting pump systems.

Inline pump controllers to avoid using a pressure tank

A third option might be to use an in-line pump controller. An inline pump controller can be added to an existing system and works with most water pumps.

The inline pump controller senses pressure changes similarly to the pressure-sensitive water pump system we described above, and turns the pump on or off as needed. Some inline pump controllers include an additional sensor to shut off the pump if the water supply is lost, thus protecting the pump from damage.

On 2018-08-08 - by (mod) - what type/brand tank less booster pump would you recommend ?

Dan, take a look at the Scala2 pump:

GRUNDFOS SCALA2 DATA SHEET [PDF] retrieved 2017/03/26, original source: http://us.grundfos.com/content/dam/GPU/Literature/SCALA2/SCALA2-DATASHEET.pdf

On 2018-08-08 by Dan P

Low water pressure, what type/brand tank less booster pump would you recommend ?

Existing conditions: private 2" well w/ jet pump/tank primed with artesian well. pumps up hill approx. 40' to cabin. low pressure .

will install booster pump indoors in heated walk-in crawl space @ inline filter location. should pump be installed before or after filter ? Thank You, Dan.

On 2017-08-20 by Kay

Thanks for your answer, I appreciate your help.

On 2017-08-19 - by (mod) - the pressure control is put close as possible to the pressure tank - livestock watering system

Kay,

Normally the pressure control is put close as possible to the pressure tank, and they decide when to turn on the pump.

Your Tee is probably way ahead of the tank and pressure control and probably also way ahead of a check valve near the tank.

So the pump won't come on to feed your livestock waterer until pressure on the house side falls enough to turn on the pump.

The livestock won't appreciate such a setup as they'd have to let you know to run water just to give them a drink.

If you don't want to feed the livestock waterer from a water line originating at the house, you'll probably need to install a second pressure tank and pressure control switch at the livestock watering equipment and wire the second system to turn on the pump as a logical-inclusive "OR" circuit - that is, either or both switches can turn on the pump.

On 2017-08-19 by Kay

We installed a self waterer for our livestock by putting a T in the line from the submersible pump to the house that has a pressure tank in it.

The self waterer will only work if the water in the house is running and has run for about five minutes. Would an inline controller be a solution and if so where would it be placed? Would it work with any submersible pump?

On 2017-07-02 by Roland Schmid, Thailand

Booster pumps in series possible?
Hello,
I need your help to verify if this installation will work.
We need to increase todays water pressure in our the 1-storage building from 2,2-2,8 bars (31,9-40,6 PSI) up to ,5-5,5 bar (65-80 PSI).

Today the Mitsubishi booster pump model WP-255QS delivers this 2,2-2,8 bars but we cannot increase the water pressure by installing a pressure tank as the Mitsubishi pump won’t work anymore (checked with Mitsubishi already).

To simply replace the Mitsubishi pump by the Grundfos SCALA2 won’t work either as SCALA2 requires a minimal inlet water pressure of 1 bar (14,5 PSI) if the SCALA2 pump operates at 4,5-5 bars (65-80 PSI). The natural water pressure from the water tank exit is only 0,15 bar (2,2 PSI).

Our installation idea is the following:

Today’s on-ground basement 1’000L tank (unchanged), followed by the Mitsubishi pump as today (unchanged) plus an additional installation of the SCALA2 (series booster pump installation).

The inlet pressure and amount of water supplied from the Mitsubishi pump to SCALA2 would match the specifications of SCALA2.

Does something speak against this idea?
I appreciate your help. Thank you.

On 2016-01-24 - by (mod) - tankless booster pump system as an adjunct to water systems using a rooftop tank

Usually I see the tankless booster pump system as an adjunct to water systems that deliver water to the building from a rooftop tank or from a municipal system with low water pressure; generally a pressure tank system is easier on the pump and thus gives a long pump life as the pump has to cycle on and off less often.

On 2016-01-23 by krisna

which is best type for home application, is it inline pressure one or with tank model. can you clarify and compare?

Question: water pump is cycling on and off,every 2-3 sec. when a tap is opened

10 Aug 2015 Dave said:
My water pump is cycling on and off,every 2-3 sec. when a tap is opened. I have replaced the switch with a 20-40 psi switch and checked that the pressure tank ( bladder type ) has 18 psi in it.. any ideas would be helpful. Tks

Reply: rock the water pressure tank gently to see if it's waterlogged

Dave:

Watch the pressure switch. It's possible that water is not entering the tank or that your tank is waterlogged and includes a pressure gauge that's stuck, giving a false reading.

Gently rock the tank (don't break any connections) and you can usually tell if it's empty (it'll be light), and similarly, if no water is entering the tank its pressure and temperature and weight wont' change.

If you are dead certain the pressure tank accepts water and is being pumped up I cannot imagine why you'd have sort cycling every 2-3 seconds. I'd be looking for an obstruction that lets water into the tank such as a bladder stuck on itself or a nearly closed or blocked valve.


...

Continue reading at WATER PRESSURE BOOSTER PUMP - tank type water pressure boosting systems, or select a topic from the closely-related articles below, or see the complete ARTICLE INDEX.

Or see these

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VARIABLE FREQUENCY / VARIABLE SPEED DRIVE WELL PUMPS (VFDs) at InspectApedia.com - online encyclopedia of building & environmental inspection, testing, diagnosis, repair, & problem prevention advice.


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