External water taps

[Vijay]

I've finished running the MDPE pipe into the floorspace (which will be below the B&B floor) and from reading another post, it occurred to me I possibly need to think about external taps at this point. I'm more than liked going to have RWH so this might not even be an issue.

 

Do you guys normally do the pipe runs for external taps in MDPE and bring them up on the external wall, or do you do internal pipe runs and bring them through the wall? I'm just thinking of airtightness.

 

Cheers

 

Vijay

[Jeremy Harris]

All our outside taps (there are three of them) are piped externally to the house in 25mm MDPE.  The pipes mainly run in buried ducts, with the exception of one where it is fed via MDPE wrapped with foam insulation and then stuffed inside a length of drainpipe (it's a tight fit!) to protect the insulation.  This was an after thought, as I'd not fitted a duct in where we wanted to put this tap.

 

The short MDPE standpipe up to one of the taps isn't insulated, and that does freeze up in cold weather, but it seems that MDPE is resistant to freezing, so no harm results (the tap just stops working when it's frozen).  As this is just the tap at the top of the drive, used for washing the car, the fact that it sometimes freezes doesn't matter.  I know from all the MDPE feeding water troughs on the farm that the stuff will quite happily withstand freezing cycles with no harm done.

[Bitpipe]

All our outside taps are MDPE off the main.

 

I wouldn't be over reliant on RWH  - if its for the garden, given you'll need it most when it's warm and dry so it wont be getting replenished. How big a tank are you planning? 

[Vijay]

1 hour ago, JSHarris said:

All our outside taps (there are three of them) are piped externally to the house in 25mm MDPE.  The pipes mainly run in buried ducts, with the exception of one where it is fed via MDPE wrapped with foam insulation and then stuffed inside a length of drainpipe (it's a tight fit!) to protect the insulation.  This was an after thought, as I'd not fitted a duct in where we wanted to put this tap.

 

The short MDPE standpipe up to one of the taps isn't insulated, and that does freeze up in cold weather, but it seems that MDPE is resistant to freezing, so no harm results (the tap just stops working when it's frozen).  As this is just the tap at the top of the drive, used for washing the car, the fact that it sometimes freezes doesn't matter.  I know from all the MDPE feeding water troughs on the farm that the stuff will quite happily withstand freezing cycles with no harm done.

 

I wasn't too worried about freezing as I would do the same as you and insulate them within the duct. I'm already doing to the water pipe under the B&B floor

 

With RWH, my initial thoughts were to have a large water tank in the loft which is supplied by the outside buried tanks. The neighbour apparently has a 4000l tank and it ran dry (they look to be keen gardeners). There is a lot of roof and the ground is clay, so probably gonna need a 5000l+ tank(s) which overflow into soakaways.

 

With an internal water tank, I assume the tap supply pipes would all be internal and go through external walls then (for external taps)?

[jack]

What's the cost of this system and its ongoing maintenance, and how many litres of water do you expect to use per annum? 

 

4000L costs about £5 where I am.

[Vijay]

Absolutely no idea yet, hoping to go down the IBC/DIY install as I'm pretty sure bought systems are horrifically priced in terms of payback

 

Than plan is to use it for gardens, car washing, toilets and possibly washing machine too, so will use a fair bit

[willbish]

I did a few calcs recently regarding RWH at it wasn't great.

Based on this 3000L system

 

Bristol Water charge for supply 2017: £1.1627 per m3

Wessex water charge for sewerage 2017: £1.17966 per m3  (£1.120 Sewerage charged on 95% of supply)

 

Water costs £2.2827 per m3

 

To install 3000L Rain water harvesting system: £3,100

 

Therefore need to use 1358m3 from RWH system before begin cost saving

 

Max rain collection due to roof size, geographical location per year:  43.68m3 (-20% for loss)

Usage of washing machine / toilet / outside estimated per year: 64.970m3

 

1358/43.68 = 31 years

 

Even if I did a DIY system costing £1000 that would be a 10year pay back. I cant justify it especially for my site where there is a reservoir less than 2 miles down the hill!

Edited November 17, 2017 by willbish

[Jeremy Harris]

I was asked about water saving measures by BC, and encouraged to install RWH.  I argued that it was pointless, as I wasn't on mains water, but there was still some convincing to do (this was with the awkward chap that insisted I needed to fit flow restrictors everywhere).  For me the only significant cost of using water for things that could be done using rainwater, like garden watering, car washing and perhaps (if I could be bothered to try and work out how to do it legally) toilet flushing.  The latter would be a pain, as it would require some jiggery pokery to maintain the required air gap separation between the house supply back up and the RWH main supply - not that easy with a room-in-roof design, as that rules out having a separate, deep, header tank, with two offset float valves, just to fill the cisterns.

 

At our old house we were using an average of around 380 litres/day for everything, so about 130m³ per year.  The cost at the moment is £2.1721/m³, so a total of around £282 a year.  I know that most of our water goes on showers, around 240 litres per day.  That leaves around 140 litres per day of possible saving.  From that possible saving I think I'd need to knock off around 40 litres for stuff that needs drinking water, so we could possibly save around 100 litres per day from an RWH system.

 

Assuming that would be the same for the new house (I don't have any way of metering the water yet) then I do know that the cost per m³ for our own water supply, allowing for a 10 year pump life and energy, filtration and disinfection cost, works out as:

 

Disinfection energy cost ~ £22/year

Disinfection UV tube cost ~ £18/year

Pump energy cost ~ £0.17/m³

Pump capital cost ~ £65/year

Replacement filters ~ £30/year

 

Adding all this up and assuming the same total water consumption as the old house (which will be pretty pessimistic, as all the outlets are set to lower flow rates) gives an annual cost for 130m³ of drinking quality water of around £157.10 per year (I'm surprised that it's cheaper than a mains supply, TBH).  Saving  100 litres per day, or 36.5m³/day, would only save the pump energy cost, all the other costs would stay the same, as none are volume-dependent. 

 

The saving achieved by fitting a RWH system would only be around £6.21 a year......................

Edited November 17, 2017 by JSHarris

[jack]

1 hour ago, willbish said:

1358/43.68 = 31 years

 

Even if I did a DIY system costing £1000 that would be a 10year pay back. I cant justify it especially for my site where there is a reservoir less than 2 miles down the hill!

 

We did something similar and the numbers just didn't stack up (I believe our water costs are lower than yours, too). Once you get pumps and filters involved, you incur maintenance time and costs as well.

[Lesgrandepotato]

Run internally then popped out in our house, but we are not a super high spec new build just a renovation. What I would add though is a hot and cold in each location. 

We have hot and cold in place for the garden shower and as a keen biker we have a hot and cold by the garage door for cleaning dirty bikes. Much nicer than ice cold water on a dark and muddy night. 

[Vijay]

15 hours ago, Lesgrandepotato said:

Run internally then popped out in our house, but we are not a super high spec new build just a renovation. What I would add though is a hot and cold in each location. 

We have hot and cold in place for the garden shower and as a keen biker we have a hot and cold by the garage door for cleaning dirty bikes. Much nicer than ice cold water on a dark and muddy night. 

 

I like that idea of hot water too, especially when I own a dog who loves mud and water lol

[Vijay]

Costs and payback are something I will obviously consider, but a 10 year payback site fine with me as I hope this will be my life home.  

 

How else could I get rid of rainwater in a clay area from a large roof???

 

So with pipes through walls, how would you make them as airtight as possible and also limit the cold bridge?  

 

I've also thought, I'm building in ICF so is it an idea to bring the pipe up inside the concrete and then through the outer skin of the ICF? Then there would be no cold bridge or air tightness issue?????

[Russell griffiths]

How is having a rainwater tank solving the problem of where your roofwater goes? 

Do you have to provide a solution for bc 

 

we have had had to do a full flood risk and rain water analysis, and they wouldn't except a rainwater tank as any form of mitigating measure. 

The reason being what happens if your tanks are full and it rains? It goes straight out of the overflow and into your drain field. 

So why not just put it in there in the first place. 

Unless you really want to flush your toilets with it it seamed like a crock to me when we did our assessment. 

[Pete]

17 minutes ago, Russell griffiths said:

How is having a rainwater tank solving the problem of where your roofwater goes? 

Do you have to provide a solution for bc 

 

we have had had to do a full flood risk and rain water analysis, and they wouldn't except a rainwater tank as any form of mitigating measure. 

The reason being what happens if your tanks are full and it rains? It goes straight out of the overflow and into your drain field. 

So why not just put it in there in the first place. 

Unless you really want to flush your toilets with it it seamed like a crock to me when we did our assessment. 

Our Bc would not accept a RWH instead of soakaways or other means of getting rid of the surface water

[Vijay]

The roof is quite a large area and that water will not go into clay. Yes the excess water from RWH goes into a soakaway, but the idea is surely that what goes into a soakaway is mimimal as the tank is a buffer. This is another reason I would like to go down the DIY IBC route, you can simply add another 1000k litre tank if you wish.

Do you guys not think it's a matter of time before water prices increase like every other service??

 

So how else do you get rid of rainwater from a large roof in clay, a lot of soakaways??

[Vijay]

12 minutes ago, Pete said:

Our Bc would not accept a RWH instead of soakaways or other means of getting rid of the surface water

 

So how did they want you to get rid of rainwater?

[ProDave]

1 minute ago, Vijay said:

 

So how did they want you to get rid of rainwater?

I really can't see you "using" your rainwater to flush the loo is going to make much of a dent in how much has to be disposed of.

 

If your land can't absorb it in some form of soakaway, then I can only assume before the house was built, you had standing water sitting as a pond on your plot?

 

[Vijay]

Apparently before the area was developed, there was a small woodlands there. Since all the topsoil has been removed and the area is clay, any rainwater or even light drizzle sits on the top for what seems like ages - so I can't see letting the rainwater go into the ground as a viable option????

[Bitpipe]

1 hour ago, Vijay said:

Absolutely no idea yet, hoping to go down the IBC/DIY install as I'm pretty sure bought systems are horrifically priced in terms of payback

 

Than plan is to use it for gardens, car washing, toilets and possibly washing machine too, so will use a fair bit

 

I spent less than £200 on my DIY IBC system (not inc. pump), however had the advantage of a exterior basement wall to protect the IBCs. 

 

Even after screening (very fine mesh bag filter) and settling, the water is murky and does not smell fresh - i would not want to use it in a washing machine without further treatment.

 

I also recall a thread on eBuild from @JSHarris that you have to be careful using for toilet flushing as bird poo washed off your roof contains micro-organisms that would not be removed by RWH system and could pose a health risk.

 

Also, if being used for internal use, you need to be able to replenish it with potable water to ensure you can keep flushing your loos and also have a seperate plumbing system for that purpose 

 

It's good enough for the garden and that's all I plan to use it for - its really there to meet planning reqs (slightly exceeds the 200l requirement), help out with the water calculation for BR and reduce usage for watering lawn etc.

 

This link shows that one hour of hosepipe use is 1000l so it could go quite quickly!

 

[Stones]

1 hour ago, Vijay said:

Apparently before the area was developed, there was a small woodlands there. Since all the topsoil has been removed and the area is clay, any rainwater or even light drizzle sits on the top for what seems like ages - so I can't see letting the rainwater go into the ground as a viable option????

 

Have you done a percolation test?  How deep does the clay go?  Could be you can get through the clay layer to something that drains.

[Jeremy Harris]

30 minutes ago, Bitpipe said:

 

I spent less than £200 on my DIY IBC system (not inc. pump), however had the advantage of a exterior basement wall to protect the IBCs. 

 

Even after screening (very fine mesh bag filter) and settling, the water is murky and does not smell fresh - i would not want to use it in a washing machine without further treatment.

 

I also recall a thread on eBuild from @JSHarris that you have to be careful using for toilet flushing as bird poo washed off your roof contains micro-organisms that would not be removed by RWH system and could pose a health risk.

 

Also, if being used for internal use, you need to be able to replenish it with potable water to ensure you can keep flushing your loos and also have a seperate plumbing system for that purpose 

 

It's good enough for the garden and that's all I plan to use it for - its really there to meet planning reqs (slightly exceeds the 200l requirement), help out with the water calculation for BR and reduce usage for watering lawn etc.

 

This link shows that one hour of hosepipe use is 1000l so it could go quite quickly!

 

 

Rainwater collected from a roof will always have fairly high concentrations of Escherichia Coli (E.Coli), mainly from bird droppings, but it could well be from any creature that has either been on your roof or eaten by one that's been on your roof (think of all the scavenging birds and their mixed diet).  Many birds also carry parasites that can be excreted as cysts, that are difficult to kill, and other diseases that can be harmful directly to humans (pigeons are carriers of psittacosis, cryptococcosis and histoplasmosis, for example, all human diseases).  Additionally, unless rainwater storage tanks are underground and kept cool, it's possible that they might become breeding grounds for legionella.

 

As a consequence, rainwater should not really get used anywhere where there is a risk of ingestion or droplet inhalation, at least not without some form of treatment.  I'm not at all convinced that toilet flushing is safe,  because the cistern will be at room temperature and so it seems likely that any pathogens may well multiply more quickly in such an environment, but mainly because the act of flushing a toilet releases an aerosol of easily inhaled water droplets, especially at lower levels, where small children may be.

 

Few modern washing machines run hot enough to kill pathogens in the supply water, and it seems likely that there will be an increasing trend to cooler wash cycles, as there has been in other countries (I believe even cold washes are getting to be normal in some countries now).  As a consequence, clothes washed and rinsed in rainwater from a storage system will probably be contaminated with a wide range of potential pathogens.

 

There are ways around this.  The use of a fine filter of 5µ or less, plus UV disinfection, should make the water safe, but such a fine filter will require pre-filters if it is to last any length of time before getting clogged, so you're probably looking at two or three filters in series, plus regular filter changes.  The UV lamp in the disinfection unit will need to be on all the time, and will last around 12 months before needing to be changed.

 

All told, I'm of the view that raw rainwater is best kept for watering the garden, and perhaps washing the car, bearing in mind that any pumped system that produces a spray carries a risk of producing fine droplets that may be inhaled.

Edited November 18, 2017 by JSHarris

[jack]

8 minutes ago, JSHarris said:

Few modern washing machines run hot enough to kill pathogens in the supply water, and it seems likely that there will be an increasing trend to cooler wash cycles, as there has been in other countries (I believe even cold washes are getting to be normal in some countries now).  As a consequence, clothes washed and rinsed in rainwater from a storage system will probably be contaminated with a wide range of potential pathogens.

 

Washing in cold water is the norm in Australia. Australians find the idea of washing in hot water a little odd.

 

I think it's partly because the climate is so warm, and the UV (on average) so high, that when clothes are dried outside - which is the case for a lot of the year - they're effectively sterilised.

[Russell griffiths]

How did you get pp without stating where the rainwater from your roof was going to go. 

Is it not a condition in you pp 

 

what did they say you had to do. 

What did you say you would do. 

[Russell griffiths]

We have some major issues with rainwater collection and it's cost a small fortune to sort out something so obvious. 

Our place is probably the polar opposite to yours, no clay but gravel so the percolation test is perfect tip a bucket of water on the floor and it disappears in seconds. 

The problem is the water table is only750 mm below the surface. So we cannot have a soakaway

 

the solution is to have a soakaway with out a top/ lid on it. 

What is this? It's a pond, the down pipes will discharge to the wildlife pond and slowly filter into the surrounding ground. 

 

I think you will will be looking at a soakaway with a larger area so it can hold the volume until it can migrate into the surrounding ground no matter how long this takes. 

[Pete]

We had to put in soakaways, all 4 of them. Our B insp suggested using the concrete rings (for ease of maintenance) designed just for this purpose but we opted for the plastic crates as we have minimum trees nearby and a standing seam roof so not alot to create a noticeable build up of sediment. We had to dig down quite a way to create a minimal fall and get at least 5 metres from the house and still have the outlet pipe near the top of the crates so you may find you will get through the clay layer. It was not part of our planning condition.