Design for low city water pressure & flow

[cgriffin12]

I am finishing up a new construction home and honestly am lost on where to start in designing a water system for my situation. Any help or advice would be much appreciated as the local plumbers in my area do not seem to deal with pumps, cisterns or any of that due to widely available city water supply.

I decided to build 2 house on a mountain and am looking for a solution to get water to both.
Water Main: pressure 35 psi with 1" meter
Main to first house is approx 50-60 ft elevation rise and approx 1,000 ft 2" HDPE water pipe
At 2" pipe end which is 30 ft from house #1 at present: 10psi with 8.1gpm flow
House #1 is a 6 bathroom home with large master shower

from house #1 it is another 800ft distance and 80 ft elevation rise to house # 2
House # 2 is a 3br, 2ba house with standard showers

House #1 & #2 are family and wish to set up a system sharing the original 1,000 ft 2" line that is already in place.

Sorry for the long post, I was thinking after reading here for a while the best option may be a 1,000 gal cistern buried with well pump and bladder tanks for each house but one plumber is trying to get me to do some type of jet pump for house #1 and is unsure what to do on house #2. He was worried about bacteria in a cistern but admitted he wasn't familiar with them at all.

Thanks in advance,
Chris

 

[LLigetfa]

It may depend on where you locate the pumps and who's electric bill it will be on. Jet pumps are less efficient than submersibles and generally produce less pressure unless you get into exotic multi-stage versions. Jet pumps are able to lift with suction but subs want to see a positive head on their intake. PSI loss for the elevation is about .43 PSI per foot so the water won't make it to house #2 on the city pressure.

Bacteria in the cistern should not be an issue unless the city water also has bacteria.

Is there power at the city water demarc or do you need to put the cistern at house #1?

 

[Sponsor]

 

[cgriffin12]

cistern was planned to be located adjacent to house #1 due to lack of electricity at water meter

 

[cgriffin12]

is there a benefit to it were to be located near the water meter?

 

[LLigetfa]

is there a benefit to it were to be located near the water meter?

No real benefit but if there was to be a separate power meter there, you could have had one sub there to feed both houses and then just pressure regulate down house #1. There would have been around 35 PSI less at house #2 than at house #1. Looking at it from the other end, there would have been 35 PSI more at house 1.

For a starting point from where to base calculations, we need to know what PSI you want at each house. Consider somewhere between 60 and 80.

Since power is at house #1, then that becomes the logical place for the cistern. Then there is a decision of how to feed house #2 from there. Considering the 35 PSI elevation loss you need to add to the desired PSI at house #2, the pump feeding it from the cistern would need to run somewhere between 95 and 115 PSI. That needs a special pressure tank, not a run-of-the-mill big box store tanks. I'm sure @valveman can spec one for you.

 

[cgriffin12]

I'm not sure exactly as i've never had to think about y water pressure, I guess I would like for house #1 to have pressure on the first level which is elevation equal to the tank to be in 70 to 80 range so that my shower heads on the second floor have above 60 also. At house #2 60 psi would be great

 

[Valveman]

I think 60/80 at the house maybe a little high, but that is ok if you want that kind of pressure. I run 50/70 with a constant pressure setting of 60 from my CSV, which is ample pressure in the upstairs shower. But if you want to run 60/80 at each house you just won't need soap in the shower. And to get 60/80, a pressure switch setting of 95/115 would be good. A submersible pump in the cistern can easily do that. And if you want a non submersible pump, a multi-stage booster will also work at that pressure. You just need a pressure reducing valve going into the first house, so you can dial the pressure down to a steady 60 or so.
It would be like this except for just needing a toilet type float valve on the city line to fill the cistern.

 

[LLigetfa]

a pressure switch setting of 95/115 would be good.

Would the CSV and tank included with the pside-kick be up for that or would you suggest something else?

As for pressure loss at the 2nd floor shower, not factoring loss due to friction/pipe size, you lose .43 PSI per foot of rise so around 5 PSI less than on the main floor.

 

[cgriffin12]

Haha, No soap in the shower, that was a good one. I honestly didn't know what pressure would be good, if 50/70 works good and will give adequate pressure for my second story that is great for me.

Which pump option is the most cost effective and will be the most durable?

Will I have any issues getting adequate flow as house number 1 will need enough flow to cover a leak time of 4 to 5 showers going at once when everyone is getting ready in the morning?

 

[Reach4]

Will I have any issues getting adequate flow as house number 1 will need enough flow to cover a leak time of 4 to 5 showers going at once when everyone is getting ready in the morning?

I have nothing to add on the pump front, but your house sounds like a good candidate for a shower drain heat recovery system. That gets heat from the drain water, and pre-warms the cold water coming into the water heater. You need a 5 ft or more vertical space under the shower drains, so that would normally mean you would need a basement... or maybe just use it for the upstairs showers.

 

[Valveman]

Five 3 GPM showers running at the same time would be 15 GPM. The PK1A kit will work with pumps up to 25 GPM. We would need to substitute a GHG2 pressure switch for the FSG2 to be able to set it at 95/115, or 85/105 for 50/70 at the house. The little 4.5 or 10 gallon tanks are rated for up to 150 PSI, but at high pressures like 85/105, they don't hold much water. I would want at least a 44 gallon size tank, because it would hold about 7 gallons at 85/105. Just need a pump that will do 15-20 GPM at say 100 PSI or 231'.

 

[cgriffin12]

Just sent you a pm valveman

 

[Reach4]

Just need a pump that will do 15-20 GPM at say 100 PSI or 231'.

How about using a multi-stage booster pump into that 44 gallon pressure tank and CSV instead of having the atmospheric tank?

 

[Valveman]

How about using a multi-stage booster pump into that 44 gallon pressure tank and CSV instead of having the atmospheric tank?

That will work fine as long as the city allows a direct connection to a booster pump and you can keep from sucking the city pressure below zero. If you are at 10 PSI at 8 GPM flow, I would expect it to go below zero when sucking 15-20 GPM from this same line, so I think the cistern storage tank is probably a must.

 

[Reach4]

If you are at 10 PSI at 8 GPM flow, I would expect it to go below zero when sucking 15-20 GPM from this same line, so I think the cistern storage tank is probably a must.

I took 1 inch meter as indicating a high flow supply available, since nominal "5/8" is pretty common. But I see your point that they may have a no-suck rule. I am not familiar with rules.

 

[cgriffin12]

I am currently trying to get my final few parts together to get the system up and running. My water line coming from the city water supply to the cistern is a roll of 2" CTS poly pipe, I am having trouble finding a fitting to attach the pipe to the tank that will allow me to also attach a float switch on the inside of the tank.
Should I be looking for a bulkhead type fitting and if so is plastic ok or should it be brass as the fittings on the 2" CTS water pipe will be brass?
Or is it possible to use a uniseal gasket type thing and just push the pipe itself through the tank and attach my float valve on the end of the pipe?

 

[Reach4]

I am currently trying to get my final few parts together to get the system up and running. My water line coming from the city water supply to the cistern is a roll of 2" CTS poly pipe, I am having trouble finding a fitting to attach the pipe to the tank that will allow me to also attach a float switch on the inside of the tank.

You don't have to run 2 inch to the float valve, do you? I would think you would bring the 2 inch pipe through a big ball valve to a manifold. You would have a pressure gauge. You would have some 1 inch PEX or CPVC filling the tank through the float valve. You would have valving allowing you to feed the city water right into your plumbing, bypassing your pressure pump. You might have a check valve in there somewhere.

 

[Gregmech26]

Hope this worked out well.