Solar panels - pumps and plumbing

OK, here's the post that I meant to write a couple of weeks ago. Since the solar panels project is huge and daunting, I broke it down into sections: Making the panels themselves, mounting the panels in a suitable location, plumbing, and making an electronic controller. The last of these is the one that Dad finds most interesting, so conversations with him about solar panels tend to end up on that topic fairly quickly. For me, that's the least worrying (and probably the most fun) aspect of the project; I need help with the other bits. Having reduced, Mounting the panels to something less scary, my next most daunting part was plumbing. This was daunting because I'd never done plumbing before.

After dithering about and failing to get started for about two years, I called Dad and asked him to come and help. He spent a week here last spring and was hugely helpful. He put a lot of pipework in place, which was great, but since I didn't do it myself, I was just as much a novice at the practical side as I had been at the start of the week. However, going through the design and planning stage with him did teach me a lot, mainly about what's actually available in terms of different types of connectors and suchlike.

Our initial design had a pump and valve (very important: With no valve, the loop is permanently open, allowing hot water from the tank to flow out to the higher solar panels whenever they're cooler, e.g. at night) in the cupboard with the thermal store, then pipes running from here out of the cupboard, over the kitchen door, through the wall into the conservatory, along one of the conservatory roof joists, and out onto the hillside. There, we'd have the solar panels and a header/expansion tank. This last item is necessary to allow the water to expand as it heats; a completely sealed system would probably explode and I don't fancy dealing with the more high-tech alternative, a pressure vessel.

I'm never keen on spending money, so we salvaged as many parts for this as we could from things I already had. When I took the old central heating system out, I was careful to coil the microbore (10mm) pipes without kinking them if I could, so they could be reused. There was quite a lot of larger pipework, too, so we had plenty of pipes to play with. I found a spare header tank in the loft. There was a dead, dehydrated bat in it. I had an old washing machine that died of rust in the drum... or somewhere... it leaked, anyway. We salvaged both pump and valve from that (helpful having a dad who's taken many a washing machine apart in his time).

We spent the first day planning how it would all go together, and listing the various connectors we'd need. Bits were bought, pipes were connected, holes were drilled through walls, the pump was tested in a bucket of water, one radiator was painted black, and the system was assembled. (This was over a year ago, so you may be getting less detail than you would have done had I written the post sooner.)

Whilst I ended up with a much better understanding of plumbing and quite a lot of pipework in place, there were two main outcomes from that experiment: 1) A washing machine pump is not powerful enough for solar panels, and 2) The position on the bank where we'd put the header tank was not, in fact, the highest point in the system. This gave me two clear tasks to do next. However, once Dad had gone home I then caught up with various other things that I hadn't been doing while he was staying... then got distracted... and so it ended up being almost a year later that I got back to the solar panels project.

In the meantime, I had managed to buy a suitably powered pump. Being generally tight-fisted, I'd balked at buying an actual central heating pump and gone for a much cheaper aquarium pump instead. This may have been false economy. As soon as it arrived I saw that I'd made a mistake. The two nozzles shown in the photo were not an inlet and an outlet nozzle, but alternatives for the outlet. The inlet was covered by a grille. Evidently this was a submersible pump. Undaunted, I removed the grille and found a plastic ring that looked like something I might fix a pipe to.

Sometime later, I actually attempted to fix a pipe to it. My first attempt was a copper pipe around the outside with PTFE tape to seal. That didn't work. Fitting a pipe inside was more difficult as the impeller was fixed by three struts. Nonetheless, this was my next attempt: I cut slots in the pipe...

I cut three of these slots

... which enabled it to fit snugly into the pump.

Looks promising, don't you think?

This time I sealed it with glue and when I filled the pipe with water, my connection proved to be water tight. Unfortunately, the rest of the pump did not. Apparently, Water tight is not a requirement of submersible pumps.

Maybe an actual central heating pump would be necessary after all. We did have one - it was in the old boiler. Ian was very doubtful about its likely performance, though. He said it was making terrible noises just before the boiler stopped working altogether. Still, given the cost of new pumps, I decided to try this one next. It wasn't easy to get out - I think the last step in manufacturing that boiler was to rivet panels to the outside, so I had to cut a pipe to get at some of the nuts.

After a happy morning dismantling the boiler, I examined my pump. The first thing I did was to connect up the wires. It hummed pleasantly and I could feel a draught of air from the outlet. That was good - it seemed to be working. Next, I looked at the connections. I didn't fancy tackling the huge nuts on the pump itself, so I took it out with the adjacent bits still attached. As luck would have it, the connection on the outlet side fitted my valve perfectly, so that one was easy. The other one was much more of a challenge than it first appeared. It was a standard compression fitting with a nut that had 18mm stamped on it, so all I needed was a bit of 18mm pipe and an 18mm x 22mm reducing coupler. I had bits of pipe...

Part of the boiler, including 18mm pipes

... but the adapter proved surprisingly difficult to get hold of. Of course, it happened to be a Saturday afternoon when I was doing this, so trade suppliers weren't open, but I searched many websites. Having drawn a blank online, I looked again at that nut and noticed that as well as 18mm it also said Flowflex. I looked them up and their website didn't have any 18mm fittings either, but I thought they jolly well ought to have what I needed, so I sent them an email. After that, I couldn't do any more for the rest of the weekend.

Come Monday morning, I tried calling a local plumbing trade supplier, who expressed bemusement at my request, No... they're usually 15mm or 22mm. Yes, I know that. Usually isn't very relevant to the nut I have in front of me. I then checked my email and found a reply from Flowflex: Yes, we still manufacture 18mm fittings, but the problem is that we can not sell to the end user, but please contact Dan at First 4 Fittings, Daniel.jones 'at' first4fittings.co.uk I share this with you, only slightly edited to avoid Dan getting inundated with spam, because if you happen to need this information (and it's possible that the wonder of Google will have brought you here in search of precisely this), you will be very glad of it. An email to Dan elicited a quote for what I needed within about ten minutes. It wasn't even expensive!

A few days later I had my coupler, and a few other bits and pieces that I'd ordered at the same time, and I was ready to fit my pump. The only trouble was, I'd soldered the pipework in place to suit the aquarium pump. I skipped over that bit earlier but yes, I did soldering, and it didn't leak! Anyway, the pipe for the inlet side was not quite parallel with the wall, and also a bit low for where I wanted the new pump. I cut it back to make more space, but still needed a pipe running at an interesting angle into the pump. I spent some time assembling a wooden mount for the pump, including a wedge to fit between it and the wall. Did you notice that the 18mm pipes have bends in them? I decided to make use of one of these to get an upwards slope, as well as angling the pipe slightly towards the wall. The final arrangement should fit, but calculating and measuring felt like too much of a challenge. I'd have to offer it up, tighten everything up, then screw the mount to the wall wherever it ended up.

This presented a problem. If I tightened the connections fully, I wouldn't be able to drill holes in the wall because the mount would be in the way. If I didn't tighten them up, I wouldn't know where to drill the holes. Also, that pump is really heavy and it needs to go high up in the back of a cupboard.

This was my workspace when plumbing.
I had bruised ribs for days from leaning across that bar.

I called Dad for advice. He fully appreciated the problem of the heavy pump. Could you fix a piece of wood underneath to support it while you work? Well yes, come to think of it, I could. I fixed up a makeshift shelf and stacked various things on it - not all wood - to support the pump in the right position. This enabled me to line it up, tighten the fittings part way to make sure they wouldn't be under strain, make small adjustments, and then mark the positions for the holes in the wall. Then take it down, drill holes, screw mount to wall, tighten up connections and connect up the other end. Luckily, the other end was connected with a bit of rubber pipe, so I didn't have to worry about that too much. You can see the shelf assembly in the photo above. Here's a closer view of the pump:

That shelf isn't actually doing anything any more. I just haven't got round to taking it down yet.

I'd already got the header tank connected up (this involved cutting a hole in the ceiling and moving rockwool. Ugh) so at this stage I was almost ready to test the whole system for leaks. I just needed to connect up the radiator outside, which I did with much PTFE tape. I expected it to leak like a sieve, which wouldn't matter for current purposes, but surprisingly it didn't. Filling the header tank involved water spraying everywhere when I tried to connect the hose to a bathroom tap, then much going up and down of stairs and the ladder once I'd reverted to the outside tap connection. Filling the system involved raiding a spare light fitting for an electrical connecter block, and an extension lead. Without power, the important valve stays closed, so a section of the loop contains a large air bubble.

I was delighted to find that after tightening the connections a little more, there were only two small leaks. One I already knew about, in the plumbing that Dad did, and one on the outlet of the header tank, where I'd twisted it a little while tightening an adjacent connection. At the same time, I felt a little flat. Yes, I'd completed a major section of the work (well, almost. I still had those leaks to fix), but I had nothing to show for it. I've now fixed the leak in the loft (but not yet the one in Dad's bit) and you'll know if you've read my previous post that I'm now feeling a bit more enthusiastic about it. The next step is to make a box so I can insulate the radiator. I might even be brave enough to plumb it in properly.