Plumbing: Fitting Input/Output Pipes Externally To A Round Pipe

[GSD4ME]

With all this sunshine I was looking at making a solar shower, as it gets very costly to use the immersion heater to warm a tankful of water for 2 people. My idea was to use a length of black guttering downpipe, sealed at both ends - (quite easy to do) with an input on the uppermost surface at the "top" end of the pipe that would connect to a hose, which in turn is connected to an external tap, so that the unit can be filled. Near to that input (to be attached to the side of the downpipe) I would connect another short piece of output hose that would hang over the edge of the roof and this would dribble out water to show that the downpipe has been filled. The bottom end of the pipe would be connected to a shower head so that the heated water can be used. The whole unit is them laid on a flat roof (part of the house) to enable the sun to heat the water. The 2 problems I am having are (1) how to connect the input/output areas to what is a round (ie non-flat)external surface of the downpipe, and (2) given that the seals should be fairly tight, how to create such a seal on the inside AND outside of the downpipe surfaces as it is not possible to get my hands inside to create the joins - do self-tapping seals exist in plumbing? Obviously a drawing would be much better here to explain my problem but a text description will have to do, alongside your imagination. Many thanks. ADB

[bhg481]

You real problem will be controlling the temperature of the water both in the pipe and at the shower head. There is a real danger than you could boil the water if the pipe is in the sunshine, particularly if you don't use it or go away for a few days - that could result in the pipe exploding. The other problem is getting the temperature at the shower head cool enough to use.

[Canary42]

You could possibly cannibalise a water-butt diverter kit going on the downpipe. Rather pricey solution though.

https://www.waterbuttsdirect.co.uk/harcostar-rain-diverter-kit.html?wgu=12579_57172_15930940324436_df6c97c47c&wgexpiry=1600870032&source=webgains&siteid=^^^204537^^^&utms_medium=affiliate&utm_source=webgains

[The Builder]

Not sure how you can control the temperature, but.................. I admire your ingenuity ;o)

If you used "Squareline" downpipe, you could use this................

https://www.screwfix.com/p/hep2o-plastic-push-fit-tank-connector-22mm/3948f
Fit one at each end, right near the opening, so that you can get your fingers in to do them up.
These tank connectors allow a simple pushfit connection to ordinary 15mm copper tube. From that, you can connect hose bibs, taps.... anything you like.
Then, seal the ends. The trouble is... I can't think of any fittings that bung up the end of a downpipe.

If you used black 110mm soil pipe instead, you'd have a lot more water, and you can get fittings to bung up the ends.
But........... you'd have a round internal surface to attach the tank connector to, so you would have to be creative with rubber seals/washers.

[The Builder]

'ang on ............... that link is for a 22mm connection. For 15mm you need these.................

https://www.screwfix.com/p/jg-speedfit-plastic-push-fit-tank-connector-15mm/11173

[KARL]

You need to give some thought to the volume of water subjected to the heating process. For a shower you should think in terms of 20+ litres or more like 30 litres. If you, as it seems to me, aim to use only water from your new installation (i.e. at whatever temperature it is at) then you need to have a capacity exceeding what one shower needs because as you drain water it will be replaced by cold water so if tightly designed to say 30 litres the second half of your shower will be noticeably cooler and the final rinse decidedly chilly. Remember that it takes time for the water to heat up. The point made about overheating is valid and you additionally need to allow for expansion of the water as it heats up. All that said, a homemade solar heater is far from being a daft idea but it is needs a bit of thought.

[KARL]

My consumption figures are based on personal minimum experience, wet-soap-rinse and employing efficiency by turning the water off during soaping, a cycle for the head and another for the body.

[nescio]

GSD4ME has already stated that there would be an outlet pipe, to show the main pipe was filled, so expansion etc. will not cause an issue. There could be an issue with the outlet pipe, if its end is lower than the main pipe - once water starts flowing out, it could act as a siphon, emptying it, unless the inlet and main outlet are closed.

[KARL]

If the intention is to use the installation as a strictly flow-through feature then I would expect any heating during the pass-through to be very limited in a plastic pipe. Any stored water will continue warming up (sunshine permitting) until drawdown starts but the temperature in a limited capacity feature will quickly start to fall. If the overflow arrangement is to be continuously/permanently open then the installation is definitely going to be a flow-through only. All but the most miserly shower heads use from 8 or 9 litres upward per minute. The pipe needs to be of sufficient length to hold/store 30-50 litres of water to offer anything but a rapidly cooling shower every couple of hours or more. The larger the diameter of pipe, the slower the rate of temperature increase. A large coil of black polypropylene water supply pipe might be preferable to a drain sized pipe because the former offers quicker heating and more chance of useful heating during flow-through as the stored water runs out. You may well end up with experimentation, all of which can be fun if willingness and patience are available. Discovering the amount of storage to aim for will be central to making a success of this.

[The Builder]

Giving it some more thought ... this is going to cost more though .....
Why not a conventional roofspace cold water tank (leave off the jacket though.)

https://www.screwfix.com/p/polytank-cold-water-cube-tank-20gallon-uk-515-x-515-x-530mm/34521

[Ryzen]

Solar thermal collector on the roof ..and a second indirect coil in the tank..it might catch on :-)

[bhg481]

Just out of interest, in the early 1970s we lived in a rented house where the only way of heating the water was either a coal stove or an immersion heater. We had a south-facing back garden so I decided I would build a solar water heater. I built a frame from angle-iron, put corrugated iron sheets inside and then made a copper matrix to collect hot water. I connected it to the hot-water cylinder and a friend made an electronic circuit which switched on a circulating pump when the water in the cylinder was colder than that in the solar heater. We got loads of hot water from it, bearing in mind there were 3 of us in the family having baths, not showers, and it certainly cut the electricity bill. Unfortunately, having used it for a couple of years I discovered that the savings in electricity would take me about 100 years to pay for the cost of building it. Soon after we found ourselves in a position to be able to buy a house, so the system was dismantled and sold for scrap.

[KARL]

When it comes to solar water heaters glass vacuum tubes are the last word. For five months of the year we use no other heating of space or water. For a further 3 months we get nearly all our hot water that way plus some space heating. Only four months annually see solar heat production making merely an insignificant contribution.