Rainwater Harvesting

EricMears

Reed_Richards wrote: »

I used to live near an old building with a huge rooftop tank; perhaps there had been a nursery there once with a requirement for a lot of water? But unless the building was purpose-built to carry the weight then a rooftop tank doesn't seem a good idea. A modern system would use an underground tank to keep the water fresh (and not get in the way) and a pump. You might have a header tank in the loft if you want to flush the toilet in the event of a power cut and save wear on the pump.

A header tank in the loft is always a good idea. 'Designing' a WC system that will only allow one flush in the event of an interruption to either power or water supplies is just plain sloppy ! But I'm afraid there are probably millions of houses that have been built that way just to save a few pounds in building costs.

My header tanks are immediately above a load-bearing wall so a tonne or so of weight in the attic is no real problem. Houses without an upstairs LBW would be a bit more of a challenge but even a small tank that allowed (say) ten flushes would be a considerable improvement on what builders consider to be the norm.

mmmmikey

EricMears wrote: »

A header tank in the loft is always a good idea. 'Designing' a WC system that will only allow one flush in the event of an interruption to either power or water supplies is just plain sloppy ! But I'm afraid there are probably millions of houses that have been built that way just to save a few pounds in building costs.

My header tanks are immediately above a load-bearing wall so a tonne or so of weight in the attic is no real problem. Houses without an upstairs LBW would be a bit more of a challenge but even a small tank that allowed (say) ten flushes would be a considerable improvement on what builders consider to be the norm.

Hmmm, much as I hate to disagree I'm not really sure I'm with you on that. The converse argument would be spending £100 or so on an emergency toilet flushing system is probably something for the excessively risk averse or those with more money than sense To be fair, it probably depends to some extent where you live and how reliable the water supply is, but at the age of 54 I've never had an unplanned water outtage so don't really consider this a big risk. And of course in a real emergency there's always the emergency "bucket and chuck it / slopping out" option (or in my case the chemical loo in the caravan).

Again, to balance this, in days gone by when the norm was to have a header tank in the loft with a cold water feed to the bath, the cost of feeding this to the toilet cistern would have been the "few pounds" you mention and made much more sense. But with modern unvented cylinders, header tanks are a thing of the past so installing one purely as an emergnecy toilet flushing backup seems an unnecessary expense and a bit OTT to me. Each to their own on this, though

I guess what I'm saying is you have to balance the cost and risk, and to me it seems to be a big cost for a small risk. So I've kept things simple and haven't installed a header tank for the toilet.

As far as my own system is concerned, in the case of interuption to the mains water supply, I still have the rainwater tank for toilet flushing, so no need for a header tank as a backup. And in the (probably more likely?) case of interuption to the electricty supply, I still have one flush (which is most likely enough for most power cuts nowadays). Beyond that, I could always just flush the toilet with a bucket of water, or in the case of a prolonged power cut (or more likely pump failure) I've designed the installation with servicing in mind so it it would only be a 5 minute job to connect the toilet back to the mains supply.

Notwithstanding those comments, there are other advantages to having a header tank for rainwater systems, but these are more based around pump operation than backup. Again, my system is so simple that I haven't really felt the need to add a header tank.

Hope this isn't too contrary - just looking at it from a different viewpoint. Fully agree with your earlier comments about how wasteful flushing treated water down the loo is, by the way.

Slinky

My OH wants our header tank removing from the loft when we have the boiler replaced, and to go with a mains pressure system as we had in our previous home. Yes it was a bit of a pain when we had water main issues, of which there were many in that area before they replaced the mains earlier this year. With 3 toilets in the house and a couple of water butts outside, I think I only ever resorted to a bucket to flush a loo on a couple of occasions, and that was when the main itself was disconnected to connect the new one up. However with hopefully better mains where we have moved to, the risk is less. The more annoying thing was lack of water to drink. Whilst we wouldn't normally drink the water from the tank, I'd do that over buying bottled, in the event of a cut to the supply.



There is of course an upside to not having a tank in your loft, the risk of it splitting and water damage to your home is decreased, which is why I think my OH wants rid of ours.

Reed_Richards

A few months ago there was a big fire nearby. The fire hoses took almost all the mains water so the pressure dropped very low; I could not achieve enough of a flow rate to make the combi boiler work for hot water. So a water outage may not be as rare an event as you think, @mmmmikey. However Eric did say power or water and it is the power outage or pump failure scenario that you are most likely to face, as you rightly identify. Sure you could use buckets of water but in that scenario I am fairly sure my other half would accuse me of wrecking the perfectly good system we had before in favour of something less reliable. Hopefully with a header tank she would not notice anything untoward.

Slinky posted whilst I was writing this. To be clear, I like mains pressure hot and cold water on tap. I would not want the risk of a header tank except as part of a rainwater harvesting system in which case I think the reward outweighs the risk.

EricMears

Living as we do 'out in the sticks', both power and water outages are fairly common. Sometimes we get a week's notice of a planned suspension of service that might last all day; more often the service just fails and it could take several hours to be restored.

We had water off for about an hour last Saturday whilst temporary repairs to a leaky pipe were done and another couple of hours on Monday for a 'permanent' (till next time !) repair. Hopefully it will be several months before our next incident - but it could be today. The particular problem with our water supply is that it comes in an asbestos/cement pipe installed in the 1920s; I doubt if many other places have quite that level of risk.

Electricity is supplied via overhead cables and we have a full day's outage every couple of years whilst nearby trees are pruned. Recently we've had a generator supplied during such work but that's unlikely to happen for an unplanned outage.

I really wouldn't want to be restricted to just one flush per WC for more than an hour or so !

The old-fashioned 'galvanised' loft tanks were well known to corrode and leak after ten years or so. The risk of a plastic one doing the same is rather less.

mmmmikey

Sounds like we're all saying pretty much the same thing - it's a question of designing the solution to suit your own environment and requirements. If my water supply was as unreliable as Eric's I'd certainly have a different view on the need for backup.

Precautions I have taken include locating everything for easy access for maintenance and buying a spare diaphragm for the pump, which is the most likely component to fail.

One "bonus" I hadn't budgeted for was hitting limestone at a depth of 750mm. I'm now digging out what will be a perfectly suitable base for widening the drive - almost indistinguishable from type 1 hardcore, just not quite as well graded. Re-using this for the drive will save £200 of skip hire and buying £200 of type 1 hardcore!

On a less positive note, the digging is now extremely hard work, I can't even pick-axe it without levering out the big stones first with a crowbar. I've added a back brace, some Deep Heat ointment and a couple of back massages to the overall cost

Off outside again now for my afternoon digging session, hopefully only a couple of days left and I'll get the tank in before the weekend's rain....

mmmmikey

Making progress with the tank installation but the b****y hole keeps filling up with water. Only ankle deep, and it only takes a day to drain and dry out, but then it rains again. You can bet that as soon as the tank is in and the drains are all rerouted we'll have the longest drought since records began.

I'm starting to soften my thinking on having a header tank, prompted by last week's power cut and a comment by Eric on another thread. Not entirely convinced but giving this some more thought (and eating a slice of humble pie while I write this).

This presents quite a challenge because I don't have easy access to the loft as it has about 400mm of insulation and not much headroom. Not too worried about the effort involved in installation, more concerned about access for servicing in years to come.

A thought is, if I put a tank high up in the airing cupboard, I'd have a head of about 1.5m from the water level in the header tank to the top of the WC cistern. Would this be enough to re-fill the cistern in a reasonable amount of time? Can you get special low-pressure fill valves and are these any good? Could I arrange this to get enough access to the header tank fill valve for servicing?

Any thoughts/comments on this gratefully received....

Thanks, Mike

markin

Have the tank in a easy to reach location and run pex.


I don't think the is any such thing as a low-pressure fill valves it will just fill really slow, As long as its higher gravity will take car of it.



Some pics of your garden and tank would be fun to see.

Reed_Richards

mmmmikey wrote: »

Can you get special low-pressure fill valves and are these any good?

The last toilet cistern valve I fitted came with two inserts, one for for medium and one for high water pressure. For low pressure you would simply leave those out. In the picture here https://www.amazon.co.uk/Torbeck-Bottom-Entry-Filling-Valve/dp/B003BNLECQ the white plastic thing at the front is the pressure-reducing insert.

EricMears

Reed_Richards wrote: »

The last toilet cistern valve I fitted came with two inserts, one for for medium and one for high water pressure. For low pressure you would simply leave those out. In the picture here https://www.amazon.co.uk/Torbeck-Bottom-Entry-Filling-Valve/dp/B003BNLECQ the white plastic thing at the front is the pressure-reducing insert.

My cisterns only came with one such insert but I couldn't leave it out as it was part of the structure (i.e. without it there the incoming water pipe would always leak. However, it was a very simple job to drill the hole out to a larger diameter.