Creating new system for 6 plex

[Mark Holoubek]

Hello all, I am in the process of tearing down 3 cottages and building a new 6 plex. The current system is a standard submersible well pump in a 44' casing that produces 10 gpm according to the well drilling company who did it off a hose bib not through the pressure tank (I will be verifying using the correct procedure). It is using the simple 20-gallon pressure tank and pressure switch methodology, which at times is overworking the pump, but since I am building a new system it is good for now. All of this is in southern WI at lattitude 43.07 and ground water temps at 50-51 degrees.

The new system plan to supply the 6 plex is to run the well pump to an 800-gallon reservoir cistern for max demand capacity and to work the well pump less often (max demand is 43.5 gpm, which will never happen but is planned for). Then through a solar water heater to raise well/ground water temp water for less required heating of dhw. Next, it would run through a constant pressure set up and then through filtration and softening system and finally to the city water meters (we are on city sewer but not water, city measures water useage to charge for sewer).

I have built a lot of buildings and done a lot of research on design but this is my first go on a system like this and would love to get the pros opinions. Therefore I want to break down the system critique in stages of the plan. Stage 1 - Well pump to reservior, Stage 2 Reservior to solar preheat to constant pressure (if jet pump), Stage 3 constant pressure to filtration/softener to meters, Stage 4 Meters to DHW boiler to units.

Stage 1 Well to reservior. I plan on using the current well pump. I believe that utilizing the correct methodology to measure the well compacity I will end up with more than 10 gpm. I will find out this weekend. The well is shallow (44') so there is limited casing reserve capacity, but will be measuring water height in the casing this weekend also just so I know exactly what I am dealing with. My submersible is only 1/2hp and my pipe is currently 60 year old 1" black poly. Based on my research the 1/2hp is suppose to max out at 14.5 gpm at 40 feet otherwise you run into maximum drawdown issues, unless the well is significantly more than 10 pgm. At 60 psi that 1" maxes out at 47 gpm, which I highly doubt that well will produce. I plan on upgrading the pipe to 1 1/2" pex off the pump to maximize through put of the pump if I miraculously have a more than 47 gpm well. Whatever measured capacity i have I will be upgrading the pipe to the reservior to pex and I most likely will be placing a check valve just above the submersible well pump, which it does not have currently. I of course need to define the well's water limit capacity and place a protection circuit on the pump so it never runs hot and out of the well's reserve water level.

The pex will go directly into reservior, no check valve. The well pump will be turned on by a flotation switch inside the reservior set to turn on after a draw of around 100 gallons occurs. This should limit the number of cycles the well pump incurs. The reservior is planned to be inside the heated envelope with in floor heat during the winter. This will start the facilitation of the temperture rise from 50 degrees to around 70 degrees maybe higher during overnight storage. The floor will be heated with 100 degree water from the boiler, Can anyone see any issues with this? (Cold water supply to the units is planned to be as close to 100 degrees as possible to limit the cost of DHW boiler demands. Cold water will be achieved through inline 10 gallon reserviors behind the refridgerator which will feed the cold water/ice dispensers. It is cheaper to cool a couple gallons of water than it is to heat it, hence the planned solar hot water exchanger tank to get the water temp to around 100 before the boilers). Since the reservior will have at least 50 percent (400 gallons) useage per day, there is basically no chance for microbiological issues if I adhere to a strict disipline of proper sealing and venting of the reservior. Please critique those assumptions. My big question on stage 1 is wheather to go with a variable rate submersible or to go with a variable rate jet pump for constant pressure. The submersible will heat the water to cool itself which is a plus, but if it needs work, then I have the need to pull it, which I guess really isnt that big of a deal since I should rarely have to pull it. Another bonus would be all connections could run out of the top of the tank. Is there something I am missing about the pro and cons of the two pumps?

The constant pressure pump wheather it is submersible or jet will have to push the water through the solar hot water exchanger manifolds (not sold on this yet) and up 20 feet vertically and another 55 feet lineal horizontally to the farthest units boiler/DW distribution manifolds at a design rate of 55 gpm (4.5 gpm more than required) at 60 psi. Everything is 1.5" pex to water meters and then 1" or 1.25" (?) to units. There of course will be loss due to filtration and softening but I have not found a source to calculate the loss yet, so if anyone has a documented resource that would be great. Filtration is planned at 20 micron and then 5 micron in series using dual stacked cartridge filtration. I guess I could duplicate that configuration in parralell if it would make a big difference in the pressure loss? If anyone knows of a better way to limit pressure loss with another filtration method I would love to hear about it? Also what pressure am I going to lose through softening? I guess that would depend on whether I use a resin bed or something like Caleffi DirtMag separator. Softening will be metered volume and timed for regeneration at night only. Based on all these losses and the research I did, it looks like I will need a constant pressure pump of 3/4hp or more. Any and all critiques are welcomed.

 

[Valveman]

I am afraid, just like your long post, you are making this way more complicated and less reliable than it needs to be. Your 10 GPM pump that will do 12-14 GPM when needed will more than likely be plenty for 6 units. Adding a simple Cycle Stop Valve to the 1/2HP pump and 20 gallon size (5 gallon draw) pressure tank would stop the cycling, making the pump last a long time, and deliver strong constant pressure to the units. Adding the CSV1A for $224.00 is probably all you need to do. If the well will make more water, you could replace the well pump with one as large as 25 GPM using the same CSV1A and 20 gallon size tank.

If you want to set up for 47 GPM you would need a cistern and a 50 GPM pump. In my opinion that would handle more than 20 normal size homes. I would still leave the well pump set up to deliver water directly to the units as a backup for when the booster pump fails, as that always happens at the worst possible time like on a holiday. I will post a drawing of how to use both the well pump and/or booster pump to supply the units.

Although constant pressure is a really good thing, how you get it is important. If you thinking about using a constant pressure submersible or booster pump, you haven't done enough research. With the variable speed type pumps you would be getting the most expensive and least reliable pumps on the market. These are made to sound cool (lots of advertising) and rip as much money out of your wallet as possible. A simple Cycle Stop Valve will do a better job at delivering constant pressure, and will extend the life of your pump system instead of shorten it the way a variable speed control does.

Also, I think it would be much less expensive to just heat the water as needed. Hot water is a very small percentage of total water used at a house. No need to heat all the water a little to keep from having to heat a little of the water a lot.

 

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[Bannerman]

Why would you want to supply 100 degree water to flush toilets? 100 degree water would be an incubator for bacteria.

Your solar heater would function more efficiently by preheating only the water supply for the DHW boiler. This could be performed using a storage tank in which cold water enters from the well. The coldest water from the bottom of the tank will be circulated through a water to water heat exchanger, heated by the solar system. The heated water would then return to the storage tank but would continue to be circulated through the heat exchanger until no further heat gain is possible from the solar system. The hottest water at the top of the storage tank would then supply the DHW boiler to raise to the final desired temperature.

An additional check-valve is not needed. There is a check-valve within the well's submersible pump.

Your current pump is capable of delivering 14 GPM from the well, but you are concerned the current 1" poly 47 GPM capacity limit will be inadequate to deliver sufficient flow from the pump???

You said the maximum design demand is 43.5 GPM, but plan for an 800 gallon tank to supply that demand. This will only provide 18 minutes operation until the tank is totally empty, not counting the 14 GPM entering from the well.

Water from a well will typically contain some level of bacteria. To determine the appropriate filtration and treatment methods that will be appropriate, a comprehensive lab test will be needed. National Labs Watercheck Standard Well package is frequently recommended in the Water Softener forum. http://watercheck.myshopify.com/?aff=5

 

[Valveman]

Couple more thoughts. If you really need 47 GPM, just install two of the 25 GPM size systems as seen in the drawing above. You could start with one and add another later if needed. It would give you a redundant or backup booster pump. It would be more efficient than one larger pump, as the flows will be low enough for only one pump most/all of the time. The only thing needed to make the two pumps work together when needed is to stagger the pressure switch and CSV settings like 40/60 and 50/70.

Also, the warmer the water in your storage tank the easier it is for contamination to grow.

 

[Mark Holoubek]

Couple more thoughts. If you really need 47 GPM, just install two of the 25 GPM size systems as seen in the drawing above. You could start with one and add another later if needed. It would give you a redundant or backup booster pump. It would be more efficient than one larger pump, as the flows will be low enough for only one pump most/all of the time. The only thing needed to make the two pumps work together when needed is to stagger the pressure switch and CSV settings like 40/60 and 50/70.

Also, the warmer the water in your storage tank the easier it is for contamination to grow.

Thanks for the critique it is greatly appreciated. Yes raising the temperature of the 800 gallon tank is an issue that I am concerned with. I think I would probably be better off placing a larger (4000 gal or more) tank underground but then I have to certify the system and perform regular testing (anything over 800 has to be certified and monitored in WI). Once I cross that 800 gallon threshold I am in that catagory anyway. I could run the dual 25gpm as you suggested and give me the peace of mind of redundancy, which is in itself worth to me. I am a big fan of redundancy. My biggest need to preheat the water was due to the fact that I was planning on only using electric on demand heater at the unit level. Which does not look to be advantageous for the loads already existing on the 200 amp panels.