Hello,
Does anyone know how you can increase hot water pressure without increasing the tank size or position or increasing the pipe size. I was thinking if there is pump that you could add to the hot water supply to increase the speed of the hot water flow. This is for an open vented system.
Many thanks Arif
A normal central heating pump can be fitted in the outlet of the hot water tank to increase the flow. But you need to fit a flow switch device that detects when the water is being demanded so that the pump isn't running continually.
Good idea in principle, but not using a standard CH pump which will rust as a result of an ongoing flow of water with dissolved air.
For HW applications, Grundfos, among others make a brass pump and this should be used.
.andy
To email, substitute .nospam with .gl
Surely you need a bronze pump not a normal £30 one??
Yes. It is called a single impellor shower pump. If you're pressurising the whole house with it, get a good quality heavy duty type such as a Stuart Turner Monsoon. Depending on the layout of the system and myriad other factors, you may find the increased flow rate leads to air being sucked down the vent tube. If this happens, and there is no obvious culprit like a half closed feed valve to the cylinder, you will need to install a flange on the system (or you might find turning the pump down fixes it). The flange will normally eliminate the air effect provided it isn't too bad, although it will effectively reduce the size of your cylinder slightly as the top of the cylinder will become "dead" space.
Christian.
To Andy and Tony.
I was only trying to help with the question the OP (Harry) posed, and the best solution I thought of was a standard central heating pump with a flow switch control arrangement. These standard pumps have lasted on our own system for anything up to 10 years, so I was not under the impression that a materials change to said pumps would create any massive increase to their performance or longevity in these circumstances.
My thoughts are that the standard pump cost is small and the length of time it lasts in this type of environment outweighs the costs of installing a more expensive pump which gives such a small increase in the life span of the unit. My research into the subject has shown me that the standard central heating pump has a life span of up to 10 years, while the bronze units are rated as having a life span of 12 years. To me, this small increase in the longevity does not justify the greater increase in cost of installing this type of pump on to a system which will not have a continual flow of aerated water, but will only supply a small amount of water over very short periods of time.
The standard pumps are fine as long as they are installed in a position which keeps them internally flooded. The water flow through the pump from a storage cylinder is not interrupted by massive increases in aerated water, so the impellor unit on a standard pump is more than capable of withstanding these small deviations and will work quite happily for many years in this situation.
So, in summary, although I disagree with the suggestions you've made on the type and construction materials of the pump required in the situation that the OP (Harry) has, I will leave it to his own research into the matter to prove otherwise.
The just of this posting is similar to a letter I have to compose to an architect. Does it sound OK ?
I think you've misunderstood the reasoning. In a CH system, the only reason the iron/steel components (pump, rads, boiler water jacket etc.) last more than a few months is that it's a closed system.
You start off with a set amount of water. In the first few weeks, all of the oxygen in this water gets reacted out. The water by then has zero dissolved oxygen, and is limited in the amount of corrosion it can cause.
But if you had a constant supply of fresh water the corrosion would carry on at the same rate. Within a few months there weill be very little iron left.
The conditions are different though. The CH pump is in iron/steel because it can be. The water is essentially anaerobic after a few days - i.e. dissolved air is driven out. With the addition of inhibitor, rusting can be essentially eliminated.
It will always be in contact with water containing quite a lot of dissolved air, even if the water has stood in a roof tank for a few hours, so it will deteriorate in a much smaller time period than 10 years.
The manufacturers make pumps for DHW and potable water use in bronze, brass or plastic (or even stainless steel) for a reason......
We're not talking about the water being grossly aerated because the pump innards are partly out of water, though. Just having it in contact will cause rusting quite nicely.
Yes it does. What do you want him to do for you though?
.andy
To email, substitute .nospam with .gl
The letter I need to write is about equipment that is going to be installed alongside other electrical stuff that will cause interference on it, so I want him to consider a change in the materials he wants used for the installation. I know that the change will greatly increase the life span of the new equipment, so I would like him to understand the benefits of changing it now before it's to late.
Ah, I see.
I wonder with architects how much skin they have in the game after the project is complete though. Do they design for form or function?
Let's hope he doesn't do airport roofs......
.andy
To email, substitute .nospam with .gl
This architect, a lady btw', has designed everything in this site, right down to the head colours of the screws that hold the knobs on the doors, and the really funny bit is, she sounds French and has the surname Le Boussier. So who knows what else she's been involved in. :-))
I have had mixed results with using iron pumps for DHW boosting and circulation. In two applications I replaced the previous iron with a new iron pump and all was well. Perhaps the water heater had managed to undissolve all the air from the water before it met the pump? In the other application I was taken with the 'its wrong but its five times cheaper and does the job' argument. I installed an iron pump only to have to replace it with a bronze one a few weeks later due to discolouration of the water.
Hi,
Installing some sort of anode upstream by the pump could help, BES part no. 12242 might do though it's zinc and not magnesium which is better. A section of 22mm or 28mm pipe with a nice big lump of magnesium fixed in it would do the trick.
Apparently these devices work for central heating systems too:
cheers, Pete.
Good point about the flange. I've been researching these. I bought a 22mm surrey flange from PlumbCenter, only to find it doesn't fit on the top of my "Superlag" cylinder (from 1991). So I plan to make my own flange - I've bought a 22mm/22mm/22mm Tee and a 22mm/15mm reducer. The T goes on top of the cylinder. The reducer goes on top of the T. I can file the reducer's insert limiter rim so I can push 15mm pipe all the way through it, and through the attached 22mm T (so that it goes under the surface of the water of the cylinder). It's not a surrey flange - the 'air free' and normal hot water positions are exchanged. But a coupleof elbows and I can sort that.
You can hear the air in the cylinder if you bang it - and your can hear it coming out the shower head. But I'm more concerned that without a flange the pump will suck air down the expansion pipe, rather than out the cylinder!
I haven't ordered the shower pump yet, but I'll go for a Stuart Turner one. Just 1 bar (that's 30ft head - plenty for me). I want a brass pump - something that won't split open and flood my house out when I'm at work. The plastic pumps from local DIY stores look too flimsy - I don't trust them - the fittings look like garden hosepipe connectors.
Alistair.
Great for the info, but can i ask, how low shoud the pump be position from the hot water drain off from the cylinder, and where can i get a flow switch device and where do you connect this device as well as wiring such an item. And is it really necessary for a flange.
Appreciate the answer so far.
Arif
snipped-for-privacy@btopenworld.com (harry) wrote in news: snipped-for-privacy@posting.google.com:
Me, too, but I've got a question or two.
I started asking about installing a new h/w cylinder, moved on to a nunvented cylinder, thence to heatbank, but they all seem a bit big and ugly for me - and all I really want is a bit more flow on the hot water; so I would like to think again about a vented cylinder plus pump.
But I'm worried about sucking air - surely if my manky flow is due to lack of head, then pulling more out will mean that the header tank will not be able to keep up, and air _will_ be sucked in, or am I missing something?
I already use a pumped shower off my cold tank, and have no problem but I'd have to empty the tank before I had trouble as I drain from the bottom of the tank. And as the hot tank is closed it seems there might be a problem.
However, I would love to give this a go as it seems more within my capabilities, and stock heatbanks seem too big for my cupboard.
So can anyone help with the practicalities - the flow detector and how to wire it; sketches for a practical system, etc?
I would like to use one pump to pressurise just two taps (its all the hot taps I've got. If successful maybe to add a shower, but that seems to be a whole new can of worms.
TIA
mike
The key thing would be to make sure that the feed pipe which goes from the tank to the bottom of the cylinder is large enough.
Probably at present it is in 22mm.
WHen I swapped out my cylinder, I replaced this run in 28mm.
Having enough bore on this pipe, means that it will be much less likely for air to be sucked down the vent pipe and into the pump.
One other thing that is important is to avoid too many sharp elbows in the pipe and ideally have none at all. This can be done by renting a pipe bender (most that are cheaply available only go up to 22mm, or alternatively what I did was to use pairs of 135degree angles with a short length of straight pipe between them. Not quite as good as a shallow bend but a lot better than a
90degree elbow.You could use a flow switch (DPS have them for 22mm) and wire it in series with a bronze pump or alternatively just use a single sided shower pump.
.andy
To email, substitute .nospam with .gl
Andy Hall wrote in news: snipped-for-privacy@4ax.com:
Tahnks for the info Andy, I _was_ missing something.
A new cylinder plus pump seems more doable.
But what's DPS, please - I presume a supplier, but Google threw up millions of Discount Plumbing Supplies/Services, but I couldn't find the flow switch stockist, and other suppliers don't seem to have them.
But considering how well my Triton pumped shower goes, a shower pump might well do; though I'd like to do it right.
In an earlier post you cautioned me against a 45 litre superduty cylinder in case there was not enough in reserve
I have a 2 bed bungalow; only a small family could live here, and there is only me and the mog; and we aren't anticipating company - do you think 45, or possibly 80l is enough? I do quite fancy the mini tank.
Incidentally, how many litres does a hot bath require; any idea?
I appreciate all your help on this, your advice is really firming out the plan
mike
HomeOwnersHub website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.