I know what you mean about the designs, struggling at the moment to work out how to shorten the plumbing runs to the taps in the bathrooms as some of the runs will be 30m+ which will take a while for the hot water to come through and very be very wasteful. I have been following this over the last 10 years and although PV cells have dropped in price, nothing much has happened in terms of practical renewables has changed
Thanks Joe95 all very useful information. Do you have details of the three port valve you used? or did you just use the sort of CH diverter valve that's used on hotwater tanks? it looks like your bill came to about £3500 for parts + £2000 labour so if the savings are about £400 a year then that's quite a long payback period - over 10 years. I'm coming from a slightly different angle, I found myself with some redundant pipes and tanks and wanted to do something useful with them that might save me a bit of money. I can understand your need for UV treatment, with a tank size of 17000 liters some of that water will be standing around for months and would get pretty manky if the bacteria were allowed to grow. I can also understand the concern for cross contamination when your rainwater tank is physically connected to the water main. I must admit I still can't understand the concern expressed in this thread about my plan for two isolated header tanks - to me that seems the perfect plan to ensure complete separation, and even if the rainwater were to somehow get into the mainswater tank, it still couldn't get into the mains itself unless it could somehow climb back up through the ball cock valve! (can bacteria pole-vault?)
An easy solution would be a 3 port suitable for wholesome water, connected to a float switch to swap between mains/rainwater. Couple of lever valves to allow for manual switching. Alternatively follow the simple rule: "if it's yellow let it mellow, if it's brown flush it down".
I like that idea, a float switch system would be much less expensive than a water level sensing unit too. 'Control' of the system is very simple and far from intelligent, it is more or less the same as a light.
I explored multiple options, including solenoid valves and ones similar to use in swimming pools, but in the end I ended up fitting a standard 3-port valve that would be found on a heating system, for ease of wiring and making fault finding easier. You will save a considerate amount of money by sourcing parts for free. The cost of copper pipe now is so extortionate you would be better using plastic or sourcing copper for free. Reading what you said in previous posts I understand you will have a large tank outside, so do you need the loft header tank? I would install a pump in an enclosure at the outside tank, run the pipework up to the current water tank, and connect all the valves and wiring there. What pump are you intending to use, I assume it will be a paddle switched pump?
May have misunderstood, but your not suggesting connecting the harvested rain water to the household cold water tank?
No - far from. I would either bring the rainwater feed up to the loft where it can be fitted with the valves and check valves, and where the mains water could be switched too, Or I would run a cold water tank feed down to the outside tank where the motorised valves and manual valves could be fitted into an enclosure. At no point would water be able to force its way into either the cold water tank or rainwater tank. Several double check valves would ensure this.
Thought so. As someone else mentioned it may be better for Hemel to just use the rainwater tank and pump to water the garden / clean the car than use in the toilet. If you are on a water meter it will probably result in the same savings
Thanks for all the suggestions. I already use rainwater for washing the car and watering the garden. One of the reasons I want to use a separate rainwater header tank in the attic is that I want to pump water up to it during the day using solar power. A header tank would also allow me to control when the pump runs. The pump I've sourced is not as quite as a would like, and if someone flushes the loo at night it's likely wake us up. I would prefer that when the loo is used it refills itself immediately from the attic header tank, and then once every day or two the pump runs to fill up the entire header tank - basically I'd rather have a pump that runs for 10 minutes every two days rather than ten times a day for 1 minute
Most header tanks start at 22 litres and toilets use around 13 litres per flush. And that capacity can be reduced by the float mechanism so even if you get quite a large tank you aren't going to get many flushes out of it without having to refill.
Sospan is right about toilet cisterns. Most are between 18-13L, with some exceptions of 6L. This is a lot of water for a header tank to supply across a day. I would imagine it running 3-4 times a day with a reasonable sized tank. Do you have the header tank already, and if so how many liters is it?
Yes, you can also make significant savings if you prove to the local water board that all your rainwater is kept on your property, and that you are not using their drainage for rainwater.
My rainwater toilet flush uses 2 fill valves, the float on each sits in a small container that is intended to stop it being jammed by other stuff in the tank see Screwfix for these. I have limited the hole in the one container to slow the flow of water out of the container, this is the fresh water fill valve. The rainwater fill valve has a small secondary water outlet that I have routed to fill the container on the fresh water valve. Now when rainwater I available and the toilet is flushed, it runs into the fresh water container and stops the fresh water entering the cistern. If no rainwater is available the fresh water fill valve operates as normal.
Careful putting another 1000L in the attic, it's a lot of weight: 1000kg, i.e. 1 tonne. I would have thought that 50 litres would be enough if as you say it's topped up automatically from a big tank at ground level.
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