TerryE Posted February 13, 2017 Share Posted February 13, 2017 (edited) I suspect that we're going to do this as two passes, the first is some heavy and at times geekish discussions. Hopefully the outcome is something that one of us can summarise There's no point in trying to go through the theory and practicalities of the flow calcs, because a guy called John Heartfield has done a good job of this on his articles: Part 1 -- The Theory, and Part 2 -- Real Systems. However, it would be good to have a structured discussion on the pros and cons / ins and outs of pipework sizing and radial vs loop or branching designs. I've been doing the calculations on my system and there is little clear benefit in going to 28mm, as 22mm will carry the heaviest flow rates and as manifold, supply and all central pipework are within a 2.4 × 0.65 × 1.4 m cuboid service area, all of my copper runs are really short. In our system the 2 × SunAmp PVs are the main limiting constraint as these will bottle out at @14 ltrs / sec at 3 bar so 2 in parallel mixing 2:1 with a cool stream will be unlikely to deliver more than 35 ltr/min in practice, but that's enough to have a shower and fill the bath at the same time. Two things that Hearfield doesn't discuss are: Dead carrying capacity. This only applies to DHW connected appliances, but it an efficiency issue. Small is good. Noise. Flow against a pressure gradient is doing work. This is shed as temperature rise or as noise, and goes up on a square law. And if you get the design wrong then pipe (and appliance) noise can be a real pain. An example of the latter is the header tank cold fill in my current house. This runs up a stud wall between our ensuite and the family bathroom in our current house. Our washing machine is an indirect feed cold-fill job and we usually run a washing cycle overnight kicking off at ~4am to take advantage of E7 plus be ready for the morning and every night from 4:00, the ballcock fill on the indirect tank sets up a pssshhhhttt on the fill riser. So laminar flow in pipes is also good = don't use devices which create a lot of noise or tight elbows etc. which cause a lot of energetic turbulent flow at high pipe velocities. So we have got our service area inthe new house on the ground floor, well away from bedrooms, and the pipe runs are short, etc. The room has acoustic insulation on all internal sides. Any other comments / views / advice that we should consider / reflect in an overview? PS. John Harvey does go into a lot of detail on noise issues, manly in Part 1 so I did him an injustice. Edited February 14, 2017 by TerryE Add Postscript 1 Link to comment Share on other sites More sharing options...
ToughButterCup Posted February 13, 2017 Share Posted February 13, 2017 6 hours ago, TerryE said: [...] However, it would be good to have a structured discussion on the pros and cons / ins and outs of pipework sizing and radial vs loop or branching designs. [...] Any other comments / views / advice that we should consider / reflect in an overview? Thanks for taking the trouble to start this post. Mixing theory and practice is an interesting and particularly useful approach - because it helps us decide why not to do something we might reasonably be expected to do. I am toying with the idea of piping cold water only round the house - to three sinks, a shower and to a SunAmp PV. Heat will supplied by under-sink heaters of some sort Why? Simplicity. And because of standing heat loss, lack of space, lower cost and maintenance. In a house built to almost PH standards, electric underfloor heating and a high spec MVHR system means that there isn't any requirement for water-based heating. So to address your final point directly, would it be possible to consider cold supply only in the overview, pease? Link to comment Share on other sites More sharing options...
Nickfromwales Posted February 13, 2017 Share Posted February 13, 2017 To Terry's points first, well, what I can add anyhoo. I've always been a fan of oversizing the cold mains pipe work throughout an install. The labour is pretty much identical, and the material cost negligible to go to minimum 22mm 'backbone' when installing generic series plumbing ( starting off large at the stopcock and reducing in size accordingly as the number of outlets diminishes ). People focus on DHW flow and delivery but simply assume that the cold will be there in sufficient capacity regardless. That's not true. Most DHW is propelled by the cold mains, ( eg cold 'in'forces the hot out of the UVC ), so if there is insufficient provision for cold flow then that will directly affect the DHW performance. It's actually even worse than that as the DHW has to travel through an appliance, and ultimately its controls, to get to the outlet, so it will incur further resistance and losses along the way. That means that cold is almost always better performing at the outlet compared to hot, varying only with the resistance of the DHW device, eg a combi will be quite restrictive vs an UVC, as a combi is typically 15mm in and 15mm out, and almost always via a plate heat exchanger, therefore adding multiple further points of resistance. Add to this the fact that other occupants / white goods will be consuming cold water at the same time as, say, a shower is being drawn, then you need to seriously think about cold water delivery, and how you will provision / mitigate these losses in flow. So, more specific to Terry's question, that's dealt with by upsizing the cold mains more than may actually be needed so as to deal with any subsequent losses that would have arisen from fitting regular / smaller bore piping. Link to comment Share on other sites More sharing options...
Jeremy Harris Posted February 13, 2017 Share Posted February 13, 2017 Just as a practical observation, this is broadly what we have, where I encountered minor problems and how things ended up. - Virtually all the restrictions to flow end up being in the DHW side, rather than the cold side - I ran 25mm MDPE into the house, then 22mm for all the cold feeds as far as the manifold, and all the cold feeds to the water heating, as far as the Sunamp PV. where possible I tried to step up from 15mm to 22mm for any pipe over a metre long on the hot side, but frankly I'm not sure it made a jot of difference given the restriction imposed by the Sunamp PV and the instant water heater. - I ran 15mm plastic from the manifolds to each room with water, with the exception that the utility room and downstairs WC share the same radial feed as they are next to each other. 15mm plastic is more restrictive that 15mm copper, but in practice that seems to be an advantage, as there's less standing pipe loss and the response time of the hot outlets is quicker. - Our incoming pressure is regulated to between 2.5 bar and 3.5 bar, and we can easily flow 25 litres/minute from a 15mm plastic pipe on the cold side, with no restriction, and no significant flow noise in the pipe work. The flow rates originally were such that we were massively non-compliant with the water usage requirements, and were told to fit flow restrictors to all those outlets that didn't have them, then submit a new report showing we were compliant with part G. - I've left the flow restrictors in place on some taps, like all the washbasins and the kitchen and utility room sinks, as they stop excessive splashing and make the taps easier to control - The water softener was a pain to plumb in, because it was delivered with pipes and fittings that were pretty restrictive. I ended up replacing them with bigger bore pipes and fittings, and now the loss through it is pretty small (it's plumbed with the equivalent of 22mm pipe now). - The shower and bath taps were to two items that were pretty poor performers with regs-compliant flow restrictors fitted, so I removed them after completion. Nothing wrong with this as we're not on mains water and so the water usage rules should never have been applied to us in the first place. The shower flow rate was around 11 litres/minute with no restrictors fitted, and, (worth checking!) the hidden flow restrictor washers in the thermostatic shower mixer valve removed. I fitted a 9 litres/minute restrictor to the shower head feed pipe that had no noticeable effect on effectiveness, but failed the test for water usage, so swapped it out for an 8 litres/minute one that did noticeably reduce the effectiveness, just to get a pass. I think I could easily live with the 9 litres/minute restrictor and may re-fit it, really just to give a useful reduction in DHW consumption. - Pipe noise in rooms away from the outlets is non-existent. The plastic pipe itself is, I think, pretty good at suppressing flow noise, and with all the pipes insulated there's no noise at all in the habitable rooms of the house. The only places you can just hear flow noise is the water meter on top of the water softener in the services room and a very gentle sound from the Sunamp PV , but even then it's not audible with the door to that room closed. 1 Link to comment Share on other sites More sharing options...
TerryE Posted February 13, 2017 Author Share Posted February 13, 2017 BTW, guys, if you have a maths or physics A level, then I really suggest that you read those two articles that I linked to or I can email you a copy that I reformatted to make it readable in printable layout. I don't want to put this up as a link as this is technically a breech of copyright. @JSHarris, this is all great stuff for me and I need to think / stew about some of the implications, and I am still getting to grips with some of the non-intuitive implications of my design, like I wasn't going to bother with a water softener, until I realised that (after a postcode search from Anglian) that we are at ~275ppm which is way above the recommended maximum for the SunAmps (150 ppm). I really can't see the benefit of putting a softener on the DCW, unless I do Jeremy's trick of wiring in a direct feed to the sink, but I will need one on the DHW side. There are also some pretty non-intuitive things like the impact of adding the PHE in front of the SunAmps. Adding an extra PHE is bound to increase the pressure drop (PD) isn't it? Well no it doesn't, and you can see why here. The PD through the PHE is tiny compared to that through the SunAmps. If the DCW supply is 8°C, to O/P of the SunAmps is 65°C and the PHE output is 18°C and the final mix is 48°C then a high flow, say 25 l/min through two SunAmps is 12½ l/min per SunAmp: The mix without the PHE is 30:70 cold : SA output so the PD of the SunAmp is 0.72 bar The mix without the PHE is 36:64 cold : SA output so the PD of the SunAmp is 0.61 bar The serial impact of the PHE is ~ 0.02 bar so the second has a higher maximum throughput as well as a more efficient use of the SunAmps. But all this exchange is helping me. My original post was more about how we collate all of this for the others who are just following down this same track and need to get up to speed. 1 Link to comment Share on other sites More sharing options...
TerryE Posted February 14, 2017 Author Share Posted February 14, 2017 OK, we aren't having the exchange that I wanted, so I think that the way that I will approach this is to write up my pipe sizing design as a blog post, and I can always revise this in the light of comments. Hopefully you guys and others like @Alphonsox who also have a SunAmp setup and the others that are tracking my plumbing thread will give me feedback to help improve it. Link to comment Share on other sites More sharing options...
Nickfromwales Posted February 14, 2017 Share Posted February 14, 2017 Can you ping a link here ( as you update the blog ) please? I just want to make sure the technical stuff stays on track Link to comment Share on other sites More sharing options...
TerryE Posted February 14, 2017 Author Share Posted February 14, 2017 @Nick, for sure. It's just that I've had to get my head around the design stuff and dumping it out Jeremy-style will be helpful for others. Link to comment Share on other sites More sharing options...
Nickfromwales Posted February 14, 2017 Share Posted February 14, 2017 Try and keep it simple for me ok ?! ?? Link to comment Share on other sites More sharing options...
jack Posted February 14, 2017 Share Posted February 14, 2017 21 hours ago, JSHarris said: - The water softener was a pain to plumb in, because it was delivered with pipes and fittings that were pretty restrictive. I ended up replacing them with bigger bore pipes and fittings, and now the loss through it is pretty small (it's plumbed with the equivalent of 22mm pipe now). I believe you have something similar to us (Dualflo, the trade version of the Harvey softener). When I looked at the "22mm full bore" connections, I was surprised to see that they included a pair of flexis with 11mm internal diameter at both ends. Given it was advertised as "full bore", I talked to the plumber (he wasn't onsite at the time) and he seemed surprised at the 11mm restrictions. So I called the supplier and explained in detail, saying that I assume we'd accidentally been supplied flexis for the smaller unit that they do. The new ones arrive and they're the same as the old ones - that's actually the "full bore" flexi they supply! The next interaction is with our angry plumber, who's been told by the supplier that since the cables weren't incorrect, they're charging him for the new ones and he plans to pass the costs on to us! We got it sorted out in the end, but I found the whole thing a bit surprising. We have four showers and two baths in our house. While baths are very rarely used (handful of times a year) and never while the shower is on, two showers running is pretty common, plus there are toilets to flush, a washing machine and a dishwasher that all might demand water at any given time. It seemed crazy that they'd spent all this time and energy running 22mm pipework all over the place, only to send it through four 11mm orifices. In the end, I just had the plumber bin the flexis and convert to 22mm pipework. Also, remember that the softener needs access to a drain, and a power source unless it's one of those that doesn't need one. Hopefully not too off topic... Link to comment Share on other sites More sharing options...
TerryE Posted February 14, 2017 Author Share Posted February 14, 2017 @jack Jeff it was really useful for me :-) Thanks Link to comment Share on other sites More sharing options...
TerryE Posted February 14, 2017 Author Share Posted February 14, 2017 12 minutes ago, Nickfromwales said: Try and keep it simple for me ok ?! Nah, I won't keep simple for you, but for normal mortals, that's a different matter. Link to comment Share on other sites More sharing options...
Nickfromwales Posted February 14, 2017 Share Posted February 14, 2017 I'd get angry............if it wasn't for your grandson looking such a handsome little chap. Awwww! Link to comment Share on other sites More sharing options...
Jeremy Harris Posted February 14, 2017 Share Posted February 14, 2017 18 minutes ago, jack said: I believe you have something similar to us (Dualflo, the trade version of the Harvey softener). When I looked at the "22mm full bore" connections, I was surprised to see that they included a pair of flexis with 11mm internal diameter at both ends. Given it was advertised as "full bore", I talked to the plumber (he wasn't onsite at the time) and he seemed surprised at the 11mm restrictions. So I called the supplier and explained in detail, saying that I assume we'd accidentally been supplied flexis for the smaller unit that they do. The new ones arrive and they're the same as the old ones - that's actually the "full bore" flexi they supply! The next interaction is with our angry plumber, who's been told by the supplier that since the cables weren't incorrect, they're charging him for the new ones and he plans to pass the costs on to us! We got it sorted out in the end, but I found the whole thing a bit surprising. We have four showers and two baths in our house. While baths are very rarely used (handful of times a year) and never while the shower is on, two showers running is pretty common, plus there are toilets to flush, a washing machine and a dishwasher that all might demand water at any given time. It seemed crazy that they'd spent all this time and energy running 22mm pipework all over the place, only to send it through four 11mm orifices. In the end, I just had the plumber bin the flexis and convert to 22mm pipework. Also, remember that the softener needs access to a drain, and a power source unless it's one of those that doesn't need one. Hopefully not too off topic... Yes, we have the same Harvey softener, but ours is badged TwinTec (identical inside to yours, though, I've since found out). We had those same 11mm bore pipes, and I fitted stainless braided proper large bore hoses to mine (IIRC around 19mm bore) then hooked it up to 22mm copper that has the three full flow ball valves needed to bypass it or shut it off for servicing. IIRC, I bought the large bore flexis from somewhere like Pipestock in Romsey (I've had very good service from them, BTW). I bought a spare complete Harvey softener on Ebay for £80, that was described as "new, not working" and found that it was indeed brand new, not even wet inside from testing, with a manufacturing date on the parts that was only a couple of months old. The suspicious thing to me was that the seller was in Woking, which, coincidentally, where Harvey softeners are made................ I tested it and found that there was a fault with the water meter on top, fixed in about half an hour because the only problem was one of the gear trains inside had been wrongly assembled. I keep it next to the one we have in service, so if there is ever a problem I can just swap them over. Link to comment Share on other sites More sharing options...
jack Posted February 14, 2017 Share Posted February 14, 2017 1 hour ago, JSHarris said: IIRC, I bought the large bore flexis from somewhere like Pipestock in Romsey (I've had very good service from them, BTW). I've had a devil of a time in the past finding large-bore flexis (particularly for our ASHP). I know there's not such thing as true "full-bore", but what's described as such is often so far off the mark as to be ridiculous if not a flat-out lie. Link to comment Share on other sites More sharing options...
Jeremy Harris Posted February 14, 2017 Share Posted February 14, 2017 I've just checked and Pipestock it was, 19mm bore flexis with 3/4" BSP ends: https://www.pipestock.com/hose-fittings/metal-braided-hose/metal-female-x-female-bsp Click on the "more info" button and the spec comes up. These are also the ones I used for the ASHP, which also needed "full bore" flexible hoses. They have an EPDM liner so are OK for potable water (the liners in our accumulators are also EPDM). 1 Link to comment Share on other sites More sharing options...
TerryE Posted February 14, 2017 Author Share Posted February 14, 2017 @JSHarris @jack this issue of when to use flexible hoses vs copper is an interesting one. The SunAmps are supplied with 2×½" (or 15mm) flexible hoses which seems daft to as the internal diameter of flexible fittings is slightly less that the equivalent copper pipe. The SunAmps give flow:PD curves up to 14l/min which a flow speed of ~1.7 m/s which is getting rather high, IMO. Surely it would be better to come out of the SA in 15 copper and jump to 22mm flexible if we really want flexible connectors. The best price so far that I've found for the Harveys Crown Water Softener is £885 inc VAT from Fountain Softeners complete with 22mm high flow install kit. BTW. Have you seem my latest blog posts giving an intro to SunAmps? Link to comment Share on other sites More sharing options...
Jeremy Harris Posted February 14, 2017 Share Posted February 14, 2017 (edited) Terry, I have no flexible hoses on our Sunamp PV, and it didn't come with any, there were just 15mm copper stubs sticking out the side to connect to, so I plumbed it in with solid pipe, the same way as a thermal store would be plumbed in. Like a thermal store, the Sunamp PV is pretty heavy, so isn't going to move anywhere. The water softener is a different issue, as the internal twin cylinder unit is quite light and just sits loosely inside the outer case, that is also the brine container. There's enough risk of movement that I thought it did really need flexible connections, particularly as it has 3/4" BSP plastic threaded fittings. I didn't like the idea of risking cracking those by any strain caused by fitting rigid pipes, so used a couple of short, large bore, flexible hoses to connect it. The hoses supplied with the Harvey units are a bit like large washing machine hoses, and apart from the small bore they were also way too long for our installation. It's worth looking around for the best price on the twin cylinder water softeners, as I think we paid less than £800 for ours. Unfortunately I can't recall where we got it from, I'll try and remember to have a look this evening to see if I can find out. I know I bought it online, and that I spent ages looking around to get the best price. As far as I've been able to work out, all the twin cylinder softeners use exactly the same internal Harvey assembly, just in a different case. The spare one I bought is a Crown, but under the lid it's absolutely identical to the TwinTec, just a different casing. Yes, I read your latest entry. Nice to see that internal flow diagram, as I still think it's a clever way to use a couple of NRVs to make a "primary" re-circulating system. Edited February 14, 2017 by JSHarris typo "that" when I meant "than" Link to comment Share on other sites More sharing options...
TerryE Posted February 14, 2017 Author Share Posted February 14, 2017 @jack @JSHarris Have either of you got a data sheet on your water softener? I am looking for the pressure drop to flow curves. I did see a couple of figures quoted on one site, and assuming the typical power curve this gives 0.0276×f2.41 kPa for f in ltr/min which is 0.2 bar at 15 ltr/min, 1 bar at 30 and 2 bar at 40, but the 2.41 seems suspiciously steep to me; the power term is normally in the 1.8 - 1.85 range. Link to comment Share on other sites More sharing options...
Jeremy Harris Posted February 14, 2017 Share Posted February 14, 2017 (edited) I'll have a look later, as I remember having to hunt around to get some good data, as I was concerned about both flow rate and maximum working pressure. I do know that, in practice, there doesn't seem to be any noticeable change when I switch the softener to bypass. The arrangement I have is a straight length of 22mm cold main, with a 22mm tee, then a full bore ball valve, then another 22mm tee, all as close together as possible on that pipe run. The tees have very short 22mm pipes connecting to full bore ball valves, and those ball valves are connected to the inlet and outlet of the softener. This means that I can close the inlet and outlet ball valves and open the one in the main feed and bypass the softener completely if I need to. If there was any appreciable pressure drop with flow then I think I'd have noticed it, as I've certainly had it running in both configurations. I'll have a look later and see if I can find the data, as I'm sure I did have a data sheet with the pressure drop info on it. As an aside, and a slight note of caution, there seems to be a potential problem if you operate the valves I have in the wrong order. It only happened once, but I'd shut off the water by closing all three valves by the softener, rather than go downstairs and turn off the incoming supply (just laziness - I was working in the services room and it was an easy way to turn the water off). The mistake I made was to open the bypass valve, leaving the two valves to the water softener closed, to pressure test the new work I'd done. I then opened the outlet valve to the softener first, then the inlet and then closed the bypass valve. What happened was that the softener valve system didn't like having a higher pressure, for just a second or so, on the outlet and it started filling the brine chamber to way over the normal level. It took me a while to fix things, by manually doing three or four regen cycles (you can manually force regen with a screwdriver in a slotted fitting on top of the meter box) to lower the brine level, then I had to flush things through with loads of water. This only happened once, and the thing to remember is to ALWAYS open the inlet valve first, and the outlet valve last, that way the problem cannot occur. There was nothing very clear in the instructions for our unit about this potential glitch, and having now stripped and rebuilt the water meter on the cheap unit I bought as a spare I can see how this happens, and it isn't something that could normally happen. It happened (I think) because the meter was just about to start a regen on one of the cylinders when I happened to shut things down. Had the valve cam not have just started to open the servo port that moves the main valve this couldn't have happened, so in some respects it was pure chance that I shut it down at the worst possible point in it's internal cycle and then made an error when opening the valves. Ours now has a notice on top reminding us about the valve opening and closing sequence! Edited February 14, 2017 by JSHarris typo, "ed" missed from the end of "connected" Link to comment Share on other sites More sharing options...
TerryE Posted February 15, 2017 Author Share Posted February 15, 2017 @JSHarris Jeremy how did you deal with the overflow (rather than the drain)? The Installation instructions state "the hose should be run downhill all of the way and terminate at the exterior of the building if possible" (as a warning pipe). My thinking is that I've now got 4 pressure relief / overflows I was think putting them all through tundishes to common waste into our stack but with a moisture / wetness detector so that I get an alarm to check them if any starts dripping. Link to comment Share on other sites More sharing options...
Jeremy Harris Posted February 15, 2017 Share Posted February 15, 2017 17 minutes ago, TerryE said: @JSHarris Jeremy how did you deal with the overflow (rather than the drain)? The Installation instructions state "the hose should be run downhill all of the way and terminate at the exterior of the building if possible" (as a warning pipe). My thinking is that I've now got 4 pressure relief / overflows I was think putting them all through tundishes to common waste into our stack but with a moisture / wetness detector so that I get an alarm to check them if any starts dripping. I ran the overflow to the same waste as the drain. Both pipes are just poked into a vertical waste pipe that comes out of the floor, at floor level, as you would with an older type of dishwasher or washing machine drain pipe. This vertical waste is swept tee'd to the vertical waste that runs down inside the airing cupboard downstairs and I already knew (from hearing the drips in the main waste pipe from the MVHR) that any water running down that pipe is audible when in the utility room, or going out the back door. I can hear the unit regenerating from just the trickle of water down that pipe too. I took the view that being able to hear dripping water was a good enough indication that there might be a problem. In fact, when the thing overflowed (because of the valve sequence thing above) I only discovered it a couple of hours later from the noise of water trickling down the waste pipe, then went upstairs to investigate and found the brine level had risen to the overflow. The pipes inside the thing that supply servo water and fill the brine tank are tiny, around 5 or 6mm OD, so the flow rate if there is a problem like this isn't that high. If I was concerned enough about it, then it would be very easy to just fit a small float reed switch, connected to a battery and buzzer, to indicate there's a problem. Link to comment Share on other sites More sharing options...
TerryE Posted February 18, 2017 Author Share Posted February 18, 2017 This is a poke to J, J, and N @jack@JSHarris@Nickfromwalesjust to read and have a sanity check on my blog post on Harveys Water Softeners and let me know if I've said anything daft. Ta. Terry Link to comment Share on other sites More sharing options...
TerryE Posted February 18, 2017 Author Share Posted February 18, 2017 And another post one design details. @Nickfromwales, does the pie chart look about right to you? Link to comment Share on other sites More sharing options...
Nickfromwales Posted February 19, 2017 Share Posted February 19, 2017 Pie? Where? ? Link to comment Share on other sites More sharing options...
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