pacific northwest cabin - potable rainwater system

hey guys new to the forum and have found some very helpful information already and I'm sure there's much more i've missed so i'll continue to search around.

I'm in the midst of designing a potable rain water harvesting system for my off-grid, solar powered cabin in the pacific northwest. I've attached a horribly drawn sketch of the existing cabin and some of the components of the rainwater collection system I have / would like.

CURRENT SYSTEM: As of now we can collect rainwater but have almost no filtering from gutters to the kitchen faucet. The current system collect water from the metal roof and funnels it to the 'small collection tank' and then we have a DC pump that pumps it up to our main 'large storage tanks' which are located on the most elevated part of the property. We then have a small DC pump that pumps it back to the main cabin for use but there is no filtering down whatsoever so the water is strictly used for cleaning dishes, etc.

PROPOSED SYSTEM: Our goal is to have potable (drinkable) water. I'm a total novice but I plan to upgrade our current system by adding the following:
-leaf eater (or similar) downspout traps to help with the initial screening of rainwater. We have 2 roofs where water can be collected from so i'll need 2
-1st flush diverter of some sort. Again will need one for each downspout.
-Some sort of filter as the rainwater enters the 'small collection tank'.
-Connect the 2 'large storage tanks'. Right now only 1 is in use. The 2nd is brand new and not connected to the system
-Install a water filtration system. Thinking about something like at the link below (Vitapur Ultraviolet Whole Home Water Disinfection and Filtration System). Has a particle filter, charchoal filter and UV all in one.
-Need a pump (thinking AC) to help with flow. Should this pump go before the water filtration system? or after?

https://www.amazon.com/vitapur-Ultraviolet-Disinfection-Filtration-System/dp/B00FQGSSWU

I know there are plenty of informed people on this forum and I'm hoping to get any/all advice you might have to help ensure I install a system that might work for our needs. thanks!

We are running ours with just the spindown filter so there is no continued expense in operating it. I have a uv light but it is broke and i never repaired it. My main concern is that no sunlight hits the water. That's all i have. While the rainwater only goes through my hot water heater (cold water side is well water) , it is used for cooking, bathing, brushing teeth, dishes, etc. We have had no health issues.

There seems to be an upfront icky concern with rainwater here in the USA. If you go to other countries the ick concern is not there, primarily because it is normal to them. They use big tanks and allow sediment to fall to the bottom. They pull the water from the middle of the tank. As far as i can tell, uv filters are not used. But i say do whatever makes you feel secure about it. Peace of mind goes a long way.

Is the system automated? Are you looking for "city type" flow,  or a basic off grid type system? A little more info on that will help. Mainly if it is a pressurized system. How to hold the pressure (pressure valve,  back flow preventer, pressure tank). Thats where filter location comes into play. At least it did on my well side of system.

The vitapure unit you show uses (I think) a long finger UVC llamp in a cylinder through which the water flows.
The UV lamp has a life span and is prone to fouling, check if it is easily cleaned/replaced.
If you have it that should be the last step before the tap and the run from the vitapure to tap should be as short as feasible.
It will also pull some power if you are offgrid.
Maybe just one potable tap with the unit directly beneath.

There are first flush tank designs to go between your down spout and your first capture tanks, to allow the roof and downspout  system to flush before delivering water to the potable system.
Think about your roof material, overhanging vegetation and level of bird droppings.  Not good to flush pigeon poop into the system.

My discussion on benefits of rainfall collection,Benefits of rainfall collection
points out micro filters and purifiers are not needed.
If you have a rainwater filter, and large tanks things will be ok.

Doug, thanks for the reply. the website i'm looking at (costco) sells the Vitapur system and also sells replacement lamps for the UV. It also sells replacement charcoal filters however doesn't sell replacement sediment filters but other websites do.

They design the UV system so that you can see when the light is on/off so you know when it's burned out and need replacing (at least that what I read about it).

We have a solar system that creates a decent amount of power, enough to run a fridge/freezer, coffee machine and other small appliances year-round so I think expect the draw from this Vitapur system to be an issue.

And thanks for the note on first flush. i've seen a few options from others on this forum that I think willl work (first flush dripper end, etc).

Douglas Campbell wrote:The vitapure unit you show uses (I think) a long finger UVC llamp in a cylinder through which the water flows.
The UV lamp has a life span and is prone to fouling, check if it is easily cleaned/replaced.
If you have it that should be the last step before the tap and the run from the vitapure to tap should be as short as feasible.
It will also pull some power if you are offgrid.
Maybe just one potable tap with the unit directly beneath.

There are first flush tank designs to go between your down spout and your first capture tanks, to allow the roof and downspout  system to flush before delivering water to the potable system.
Think about your roof material, overhanging vegetation and level of bird droppings.  Not good to flush pigeon poop into the system.

Thanks Wayne! We've got 2 large black polyethylene tanks so sunlight shouldn't get in those. It's a basic off grid type system we are installing but we do have decent solar power already installed.

The pressure issue is one I'm still working on. The tanks will be situation about 10-15 feet above the main cabin so right now we do get a gravity feed but pressure is not good enough for our on-demand hot water heater (propane) to kick in. We currently have a DC pump that help improve pressure so that the hot water heater works. We plan to switch this pump to an AC pump now that we have a new solar system and have converted the rest of the cabin to AC. Wondering what other considerations / info I need to sort out to ensure the pressure is sufficient. Do most AC water pumps come with a back flow preventer or is this someone I need to specify? Do I need other components to ensure there is enough pressure? Again, sorry for the novice ?'s but that's where I'm at :)

wayne fajkus wrote:We are running ours with just the spindown filter so there is no continued expense in operating it. I have a uv light but it is broke and i never repaired it. My main concern is that no sunlight hits the water. That's all i have. While the rainwater only goes through my hot water heater (cold water side is well water) , it is used for cooking, bathing, brushing teeth, dishes, etc. We have had no health issues.

There seems to be an upfront icky concern with rainwater here in the USA. If you go to other countries the ick concern is not there, primarily because it is normal to them. They use big tanks and allow sediment to fall to the bottom. They pull the water from the middle of the tank. As far as i can tell, uv filters are not used. But i say do whatever makes you feel secure about it. Peace of mind goes a long way.

Is the system automated? Are you looking for "city type" flow,  or a basic off grid type system? A little more info on that will help. Mainly if it is a pressurized system. How to hold the pressure (pressure valve,  back flow preventer, pressure tank). Thats where filter location comes into play. At least it did on my well side of system.

There are self contained 110v pumps that include a pressure shutoff and pressure tank.  They are relatively inexpensive.  I know harbor freight has them. A backflow preventer is not included but is a must. Otherwise the pump will constantly turn on/off. It shuts off when pressure is reached, but the pressure pushes the water backwards when pump cycles off. Which turns the pump back on. Its a head scratcher. Lol. Backflow preventer cures the problem.  They are inexpensive. You just have to know it is needed. If your tank runs dry, this unit will not shut off. It's cheaper than my next example, can give you on demand water with out flipping a switch, but will burn up if ran dry.

If you go with the groundfos like in my thread, it is the only thing needed. Backflow is built in. The other thing about the groundfos is it turns itself off if tank is empty. The motor will not burn up. It will try to repressurize every few minutes.

My guess is $150 for cheaper pump with built in pressure tank and $700 for a groundfos. You would have to burn up 4-5 cheaper pumps before the groundfos is of better value.  Reliability and actual pressure-groundfos wins. Ive had the same unit for probably 7 years or longer. My guess is the cheaper one being a 1-2 year kind of reliability.

We also install an air tank on those pumps to stop stop / start cycles.

Around here, quite a number of people use one of the filter systems which sits on the counter and you fill up from the top and it gravity feeds to the bottom where there is a spout for drinking from. They look like this. The filters are replaceable. They work well and are easy.


We have a water society on island which 60 or so people tap into. It is gravity fed from a lake. Lots of people use it on their gardens and lots use it for household use. Many might filter it for drinking. Many do not filter it.

So my suggestion is to keep it simple. Filter only what is required.

Here is a pic of what i referred to as the cheaper version. The good thing is I do not think there is residual electricity while it is pressurized but ofg. It kicks on when the pressure switch trips it on. If i am.wrong, someone please correct me.

The groundfos is always using a little, even when pressurized and not running. There's an LED light that is on when it is on.