Off-Grid Rain Catch Upgrade – 5 Tiny Houses, 1 Pump House

Long-time lurker, first-time poster. Huge thanks to this community – your past advice has been invaluable.

The Situation:
Our off-grid property runs on rain catchment with a small pump house and filtration system that's worked perfectly for 8 years. We're now adding 5 tiny houses (composting toilets + ultra-low-flow fixtures) and need to upgrade.

The Plan:
Originally considered a second uphill pump house, but expanding the existing one is much easier. I've already bought some components but am open to swapping if needed.

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What I Need Help With:

1. Pressure Tank

· AI suggested: Amtrol Well-X-Trol WX-255 (81 gal)
· Thoughts?

2. Pump

· Need constant 50 PSI @ 15–20 GPM for 5 tiny houses
· AI recommended: Grundfos SQE (VFD) or Grundfos Scala2 (floor mount)
· Which is better for my setup?

3. Filtration

· I currently have a Pelican/Pentair PUV-7 (7–16 GPM). Can I keep it?
· AI suggested adding:
 · 50-micron pre-pump sediment filter
 · 5-micron fine sediment filter
 · 5-micron carbon filter
 · 20 GPM UV (after carbon)
· Will my PUV-7 work as the UV stage, or do I need a higher-flow unit?

4. Transfer from Downhill Tanks

· Main tank is uphill; larger storage tanks are downhill.
· Plan: Use a float switch + small solar pump near downhill tanks to top off the main tank.
· Should I use a submersible or external pump? Brand/model recommendations?

5. I am a novice!  Any missing parts or regulators that would make this more efficient?
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Photos attached: pump house, water tank, property map with expansion layout.

Thanks in advance for any guidance!

PICTURES
1. Property water map/plan
2. Main Pump-house and 2500g tank
3. 4. & 5 Uphill tank and pump assembly. Never used this… (Good parts if needed)
6. Inside mail pumphouse - working well for 8 years
7. Utility hub 1 of 5

Many questions and comments;
- Why blue tanks?
- We have mist green ones in Australia, they hide!
- 5000 gal tanks  would be better located near the workshop for a start, and near the house.
- The uphill tanks do not look like both being 5000 gal.
- How will water get to the tanks up hill?
- What roof area is in the cabin?
- can the wet system on the cabin be emptied and cleaned out?
- What is the roof area of each tiny house?
- Are you mixing well and rainwater in the same tanks and pipelines?
I would suggest some changes;
- separate smaller tank at each tiny house, say 2000L capacity, fed from system and each tiny home.
-What is the average rainfall in the area?
- What is the planned distance between the tiny homes? I see the 100ft scale
- Are they too close?
- separate pressure pump and maybe not a pressure tank at each tiny house, run off solar perhaps?
- what power source is planned for the tiny homes?
- 12V water pumps are used on RV's, they would be adequate for a tiny home.
- What is the elevation of the hilltop tanks above the tiny homes?
- Can you gravity feed the water to them?
- 81 Gal pressure tank seems too big.
- I doubt you will need 50psi / 50 gal per minute available water at each tiny house.
- Filter water when it comes from the tanks, not before it enters the tanks, because you will get some sediment dropping out in the tank and water can self clean to an extent.

Thanks so much for the response!
 Great questions.  Texas and Australia have much in common!  We’ve had no rain and it’s scorchin hot outside! Upper 90’s for weeks!  LOL

Why blue tanks?  I just liked the color! We have people over and I like to show off the water storage and rain catch system. I painted them to help protect the plastic from UV.  

We built our pump-house years ago beside our original 2500 gallon tank. (This is Green on the map) This tank is filled from a 600 sq ft roof. Now we are expanding and we use the larger tanks as backup storage to keep this main 2500 gallon tank full. Our wet system is easily maintained with a first flush diverter and a clean out.

We have two large tanks at the entrance (high ground on the left side of the map) for the delivery truck to deliver water if we run out. Because these are up hill, we can  attach a hose and refill the 2500g tank with gravity as needed.  My original plan was to setup a filter and pump here to supply the tiny houses that are down the hill. I have several pictures of the pump system that I started to assemble here.  They have not been used yet, just collecting dust. The tiny houses are separated about 100 feet apart to give everyone some privacy.

We also have two new 5000 gallon tanks at the lower end of the property (far right on the map) these will be fed by the new 2000 sq ft roof.  They had to be separated that distance for the wet system to overflow into the tanks. The top of the tank is just lower than the roof line. I thought we could set a small solar pump on these large tanks and use a float switch in the 2500 gallon tank to transfer water just using a small line.

We do not have a well, just rain catch. 39 inches per year average

- The tiny house parking spots have full hookups. 50, 30 and 20amp outlets.  I have to provide filtered water to these sites. That’s a great idea to put small rain catch tanks by the tiny houses, I could use that for landscape irrigation.  

Right now we use a 12V water pumps to run our water all over the property! But if we have 5 tiny houses in the future, we need to be able to meet peak demand. I think that is why AI recommended the 81 gallon pressure tank and 50 psi.  I agree that is probably overkill.  With compost toilets and low flow showers, the highest use appliance may be a small clothes washer. But if everyone used the water at the same time….

- What is the elevation of the hilltop tanks above the tiny homes?  We have a 30- drop across the property
- Can you gravity feed the water to them? Yes

I was preparing to build the second pump house at the top of the property and my wife suggested I just expand the existing pump house we already have and supply everything from that location.  Then we can just pull water from where ever we catch it to keep the 2500g tank full.  What do you think?
 Once again, I really appreciate your input!!

Some thoughts;
- the workshop could drain off the roof and straight into tanks next to it, and that would save a long sealed stormwater pipe underground.
- That water would also be closer to the uphill storage tanks.

I was preparing to build the second pump house at the top of the property and my wife suggested I just expand the existing pump house we already have and supply everything from that location.  Then we can just pull water from where ever we catch it to keep the 2500g tank full.

 I think a 2nd pump house next to the uphill storage will be better.
Because;
- If the tiny homes are fed from those upper tanks, a smaller pump would suffice to do that job.
- Moving pressurised water from the existing pump site up the hill and to the Tiny homes will need a bigger pump and a longer length of bigger diameter pipe.
- Moving water from downhill to the upper tanks with a single bigger rising main will be more efficient, with less stops and starts of the pump.
MATCH THE PIPE DIAMETER, WATER PRESSURE, LENGTH OF PIPE AND VOLUME WITH THE PUMP. WE USE CHARTS TO SORT THIS OUT AND A DECENT PUMP SHOP WILL UNDERSTAND.
THIS CAN BE USEFUL WHEN MOVING LARGER VOLUMES OF WATER BECAUSE IT WILL SAVE POWER IF DONE RIGHT.

We also have two new 5000 gallon tanks at the lower end of the property (far right on the map) these will be fed by the new 2000 sq ft roof.  They had to be separated that distance for the wet system to overflow into the tanks. The top of the tank is just lower than the roof line. I thought we could set a small solar pump on these large tanks and use a float switch in the 2500 gallon tank to transfer water just using a small line.

I would move those tanks adjacent to the workshop, and move water from them to the uphill tanks, and drain from there to the 2500 gal as needed.
I would not use the wet system from the workshop, its more that can go wrong!

Those are great suggestions!!
 Thank you so much. It has not even occurred to me to move the tanks up by the workshop. I think you might be right about that being a simpler, more effective system. And I agree about the pumphouse at the top of the hill. I do think that would be a simpler system and it would give us some redundancy, instead of depending on one system that can fail.
 Stay tuned and I will let you know how it proceeds!
 Best wishes, Kyle