Posted By Clark on 05 May 2012 10:45 AM

Posted By FBBP on 05 May 2012 10:28 AM
Clark - you could build a 2 to 3" berm around your sump pit to stop the flow of sediment into the pit and then clean out the cistern as needed. Remember that you will be going into a "confined" space and that the debris can give of gasses. Vent well prior to entry!

That's an idea I hadn't considered.  Should the "berm" be solid or porous?  I'm thinking maybe a fine mesh screen encircling the sump to block the silt, but still allow water to enter the sump?

How often do you guys have to clean out your cisterns?

I would make it solid. Yes you would lose a few inches of water but its the fines you don't want plugging up the irrigation system. A standard mesh inline irrigation filter will look after any floaties.
If you already have your membrane in place, I would just mortar a ring of bricks around the sump.
The amount of times you need to clean it will depend on a number of site specific issues. Are you set up to dump the first ten gallons or so? Do you have a filter prior to the water entering the the cistern?

Posted By FBBP on 05 May 2012 11:18 PM

Posted By Clark on 05 May 2012 10:45 AM

Posted By FBBP on 05 May 2012 10:28 AM
Clark - you could build a 2 to 3" berm around your sump pit to stop the flow of sediment into the pit and then clean out the cistern as needed. Remember that you will be going into a "confined" space and that the debris can give of gasses. Vent well prior to entry!

That's an idea I hadn't considered.  Should the "berm" be solid or porous?  I'm thinking maybe a fine mesh screen encircling the sump to block the silt, but still allow water to enter the sump?

How often do you guys have to clean out your cisterns?

I would make it solid. Yes you would lose a few inches of water but its the fines you don't want plugging up the irrigation system. A standard mesh inline irrigation filter will look after any floaties.
If you already have your membrane in place, I would just mortar a ring of bricks around the sump.
The amount of times you need to clean it will depend on a number of site specific issues. Are you set up to dump the first ten gallons or so? Do you have a filter prior to the water entering the the cistern?

Okay, I agree.  A 2" high solid "berm" around the sump might block 95% of the sediment from entering the sump if the cistern is cleaned regularly.  How often will have to be determined once the system is put into operation.  I would like the berm to be removable, so that when I clean the cistern, I can sweep the sediment build up into the sump and pump it out with a separate pump that can handle solids.  I'll also install a filter in the line from the cistern to catch any matter that gets drawn into the pump.

I have fine screen gutter guards in place to prevent leaves, sticks, roof aggregate and other debris from entering the drainage lines.  I also installed a SafeRain first flush diverter to discard the first several gallons of polluted water from the roof and drain lines.  Here's a shot of the first flush valve installed in a drywell pit hidden below the patio.




Thanks for the help.  --Clark

In case you're interested, the photo below shows the 1/2 HP submersible pump (Simer 2845G-12) with the DIY flow sleeve attached.  I used a section of 4" thin wall sewer pipe to construct the sleeve.  The sleeved pump will rest on the bottom of a 2' sump in the bottom of the cistern.  I capped the bottom of the sleeve and cut three 1-1/2" holes 6" from the bottom for water inlets.  Hopefully, that will lessen the uptake of any silt in the sump that gets past the 2" silt berm surrounding the sump as recommended by FBBP.  The sleeve is sealed at the top with a rubber gasket and clamped with a stainless steel hose clamp.  Three screws center the bottom of the pump in the sleeve leaving a uniform 1/8" gap around the motor for water to flow past the motor to the pump thereby cooling the motor.  The total cost to make the sleeve was about $15.

Posted By ICFHybrid on 04 May 2012 11:57 AM

I like filters. I use a gross (coarse) filter with a serviceable screen before the pump to protect the system and two filters following that to protect the bladder tank, plumbing and fixtures. We see the water in the toilet bowls and in the washing machine rinses, so having it come in clean is preferable.

ICFHybrid,

Do you have an automatic backup for your cistern water supply to toilets and laundry?  If so, how did you plumb these fixtures so that cistern water doesn't contaminate the backup (potable) water?  I'm thinking a double check valve on the backup water supply line to a tee with the backup and cistern water both entering the tee which branches to supply to the fixture (see figure).  When the cistern water pressure drops below the backup water source pressure (cistern runs dry), the backup water flows to supply the fixture.  Of course the cistern pump start pressure needs to be set above the backup water pressure for this to work.  Do plumbing codes allow this arrangement?  --Clark

Do you have an automatic backup for your cistern water supply to toilets and laundry? If so, how did you plumb these fixtures so that cistern water doesn't contaminate the backup (potable) water?

That's still an open question for me. Right now I have it set up so that I have to do a manual fill if the alarm indicates a low level in the cistern Haven't had to do that yet. I have a manual valve and my argument against cross-contamination would be that the municipal water is always at a higher pressure than my rainwater system. I am also 400' down a 1-1/2" line and an additional 600' down an 8" main before the nearest neighbor. I have briefly looked at a couple of all-in-one rainwater solutions (usually from Australia) that handle it automatically, but I didn't look too closely at how it was accomplished.

I have a manual valve and my argument against cross-contamination would be that the municipal water is always at a higher pressure than my rainwater system.

I'd say normally true but not always. So at least use check valves to avoid getting into the municipal water supply business.

I believe most authorities would require double checks similair to that which is required for a water feed to a boiler. Clark, in your diagram you would also need a check valve on the cistern supply to prevent the potable from filling the cistern. (might be included with the pump already.) Also with regard to pressure differentials, the system must be fool proof when there is no pressure on the potable side, say the utilities have shut down the city mains for repairs etc. With no city pressure, cistern water must not be able to contaminate either your potable inhouse lines or the city mains. Once a some bugs get into the system they can reproduce quickly and normal chorine levels may not be enough to kill them off.

Also I'm somewhat surprised that any authority would allow untreated water for laundry.

I believe most authorities would require double checks similair to that which is required for a water feed to a boiler.

I'm sure that is correct.

With a manual valve, though, you wouldn't even be operating it until rainwater system pressure was zero and there was demonstrable pressure on the muni side.

Also I'm somewhat surprised that any authority would allow untreated water for laundry.

Lovely soft rainwater, you mean.

Posted By ICFHybrid on 10 May 2012 11:48 PM

I believe most authorities would require double checks similair to that which is required for a water feed to a boiler.

I'm sure that is correct.



With a manual valve, though, you wouldn't even be operating it until rainwater system pressure was zero and there was demonstrable pressure on the muni side.

I'm thinking they might tell you that this doesn't allow for human error ;-)

Also I'm somewhat surprised that any authority would allow untreated water for laundry.

Lovely soft rainwater, you mean.

yep. That nice soft rainwater c/w bird droppings etc. (the fact that humans have used these systems for a few thousand years doesn't seem to have much impact on the Authorities having jurisdiction.)

More work about the well as a pressured water source to 75 psig systems has , and I think not unusually so, has had inspectors check for any drains to have ck/break-adapters for hoses. Also inspectors do demand DOUBLE checks at ANY pressure going to lawn sprinkling/irrigation. They argued that bacteria can 'crawl' upstream into pressured and single checked systems quite easily in 10 years.
and not just 2 check valves , but it is a requirement to have that one for side vented with an affixed drain off that side, also 2" clear at the termination drain as an air gap like for all condensate and water softener drainage codes to be followed.

I'm thinking they might tell you that this doesn't allow for human error ;-)

It would be sorta interesting to know when was the last time a residential rainwater system contaminated municipal water in the US.

USGS Volcano Hazards Program - Actions to take for ash fall If you use a rainwater collection system for your water supply, disconnect the tank prior to ash falling. Care should also be taken to avoid further contamination during the emptying, cleaning, and maintenance of vacuum equipment. volcanoes.usgs.gov/ash/todo.html -
More from this site -
Similar pages [ Result from Blekko ] Japan's nuclear contamination spreads to more U.S. states - CNN.com Mar 29, 2011 ... Japan's nuclear contamination spreads to more U.S. states ... Tom Corbett said rainwater collected Friday from his state's nuclear power plant ... www.cnn.com/2011/HEALTH/03/28/radiation…index.html -
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Similar pages [ Result from Google ] RAINWATER HARVESTING - M.P. Pollution Control Board In the present scenario management and distribution of water has become centralized. People depend on government system, which has resulted in disruption of ... mppcb.nic.in/RWH.htm -


that was more fun than interesting~

So, is Japanese nuclear contamination or bird droppings a bigger threat to rainwater systems?

Inspector will say birddroppings, ~ so I will show him the 5 Cockatiels and Finch and my lungs from a couple other dozen birds... to show him nothing affected me in ~ 55 years of such...

it IS late, and I know because I laughed hard at your sentence! T's.
g'night. EST !.

(that bacteria crawled into bed faster than me)

My city requires a "Reduced Pressure Backflow Preventer" to isolate the irrigation system from the municipal water supply. These valves are big and expensive. I have one installed. My cistern water supply ties in at the outboard side of this valve. In talking to the inspector, he was more concerned about lawn chemical contamination than bacterial contamination . Chlorine is murder on bacteria.

To supply toilets with non-potable cistern water with a municipal water backup, my understanding is that a double check valve is allowed in residential applications to isolate the two systems if a potential health hazard does not exist. The question is: What constitutes a potential health hazard? Does a private well or rainwater cistern fall into this category? Clark

Clark:
'lil mo drip---,,,
Statewide, we have been told by inspectors the MAIN reason city and well are required by code to get any check-device, and on (low near-the-flooring ) drains out of water tanks is b/c of BACTERIA. This bacteria referred to is that which proliferates easily in HOT WATER SYSTEMS on chlorinated city waters in tanks and under 125F deg, and 130F is 2010 code, in some counties (at the tap 125). (some 132F, technically by our local inspector, at the top of the tank setting , if a 'smart-stat tank' for at least 125 at any HW tap)

harvesth2o.com/rainwatercollection.shtml

[quoted]
When I expand the system to provide potable water, I'll need to install a UV filtration system before the second pump. The three-way valve and unions will allow me to do this easily and efficiently.

Because our system is interconnected with a municipal water source, it was required to have a high-hazard pressure relief valve,also known as a back-flow preventer. This valve ensures no tank-stored water can enter the city water supply. Regulations vary from city to city, so check with your local water municipality first to see what type of valve they require, if any. . I installed the relief valve near the front of the house, so when I start using rainwater for our household needs I will not have to relocate it.

The sprinkler junction or valve box, in which city water lines join with rainwater system water lines, may also require a permit. I used two standard-sized in-ground sprinkler boxes. One box holds all the sprinkler valves and the other the system interconnections. This is primarily, a three-way electric valve made for swimming pools that connects the tank and city lines with the outgoing line that feeds the irrigation system. I initially used a sprinkler system valve instead of a pool valve, which was a mistake. Sprinkler valves are low-cost and widely available, but only work one way and only when there is pressure in the line. I also installed a double check valve in this box to prevent tank water from entering the house. I will take out this valve when I install the UV filtration system. Screw-in couplers and manual off/on valve are on both sides of these valves enabling easy removal.


more homepower.com/home/

Sterile to pasteurization www.ehow.com/how_5903726_convert-rain-water-drinking-water.html

foreign www.waterpreserve.co.za/

COMM wahaso.com/rainwater_system.php?gclid=CI7XsNuC_a8CFY_J7Qodmz3GHA

I'm not sure I understood all that. I'm coming to the conclusion that the only acceptable cross connect from a private rainwater harvesting system to a public water supply is by means of an "air gap" or a RPZ (Reduced Pressure Zone) backflow prevention valve. Any other type of check valve is not acceptable because a rainwater cistern is considered a potential health hazard. Am I getting close? --Clark

The following diagram shows the way I propose to cross-connect the rainwater cistern with the city water supply.





The isolation of the municipal (potable) water from the cistern (non-potable) water is accomplished by a reduced pressure back flow preventer (labeled RPZ).  When rainwater is available, it will be supplied to the irrigation system and the toilets at 45 psi.  The RPZ will prevent rainwater from mixing with the potable water.  When rainwater is not available (when the bladder tank pressure drops below 40 psi) city water at 40 psi will flow to feed the irrigation system and the toilets.  City water pressure is reduced by about 10 psi on the output side of the RPZ.

Does anyone see a problem with this design? 

Clark - I'm not sure you need the pressure reducing valve on the cistern side, just set the 45/65 to 35/45. Another way to do it would be to use a set of floats and a auto valve to maintain the bare minimum water supply for the pump in the cistern. Let the potable water in through an air gap and you would never have to connect the two systems.

Posted By FBBP on 13 May 2012 08:27 PM
Clark - I'm not sure you need the pressure reducing valve on the cistern side, just set the 45/65 to 35/45. Another way to do it would be to use a set of floats and a auto valve to maintain the bare minimum water supply for the pump in the cistern. Let the potable water in through an air gap and you would never have to connect the two systems.

Thanks for the response, FBBP.  Never physically connecting the two systems has its advantages, and I did consider the air gap cross connect approach that you suggest.  I decided against it for three reasons:

1.  When the cistern is taken out of service for any reason, e.g. for cleaning or repairs, the toilets cannot be flushed normally.

2.  When the cistern empties, refilling the cistern with potable water and then having to consume electric power to pump it out was something I wanted to avoid.

3.  I already have the RP backflow preventer valve as required by the city to isolate my irrigation system from the city water supply.  Implementing the air gap method would cost extra.

My reason for the pressure reducing valve was to keep the water pressure to the irrigation system at around 40 psi.  The sprinkler heads will work best at a steady water supply pressure.  I'm also concerned that setting the pump pressure switch to 35/45, if that is actually possible, would mean more rapid on-off cycling of the pump and, therefore, shorter pump life.

--Clark