Does anyone know if these
I'm going to test our incoming pressure/flow rate before going much further, but, I suspect it's too low right now without some assistance.
TIA
You can't use a pump on a mains pressure tank, only on the output from a gravity fed tank, otherwise your pump could be "sucking" on the mains, something that's strictly forbidden.
If your mains pressure really is that poor a pressurised HW tank isn't appropriate.
Tim
Yep, spot on.
The only solution I can think of in the case of really poor mains supply is to have a large stored cold water supply[1] (cold water tank) and to pump both hot and cold to the outlets. Hot feed to be pumped on the outlet side of the hot water cylinder.
[1] Sufficient to supply the whole family/occupants peak demand with only limited reliance on topup from the mains.
The blurb on that pump seems to indicate otherwise, they say it's permissable to "suck" providing you don't exceed 12l/min.
All sounds very dodgy to me. How does it prevent sucking contaminated water in (from a poor underground joint or split say)?
I would get professional advice and not rely on manufacturer's information. Even if it is legal, I wouldn't want one.
Tim
Professional advice = whom? I thought the internets was a reliable source ;)
I was told about this device by my plumber.
Conventional wisdom says that you are not allowed to pump directly from the mains on the grounds that if you introduce negative pressure on it, then contaminates could be drawn into the water supply via leaks etc.
However this pump would appear to be a slightly different proposition.
Looking at:
One downside would seem to be it includes flow regulation limited to 12 lpm which is not great. It will be enough for a moderate combi, but would not take any advantage of the flow capability of an unvented cylinder like a megaflow.
Yup that would be the first step.
If you actual static pressure is below 1 bar, then that is a problem which you can contact your water provider to fix, since there is a statuary minimum they need to provide.
If the static pressure is ok, but the flow rate is limited (long narrow supply pipe to the property for example). then the traditional solution is to either relay the pipe with something bigger, or if that is not possible, to fit an accumulator. This creates a buffer that you can draw water from faster than the supply can replenish it (for a time anyway!)
Apart from all the above about negative pressure (which is correct). There are a few things to do first. Check with a neighbour(s) and see if they have the same problem. Check that all valves and stopcocks are opening fully (by disconnecting the outlet pipe and seeing how much water is delivered) Valve innards can collapse, just working the handle is not enough.
If the mains water pressure/volume is low, you might be able to get the water company to fix it at no charge.
They fitted a new supply pipe to my neighbour's house for free a couple of years back.
you could just have 1 pump on the outlet of a large cold "buffer" tank (ground level if space exists?) then it can supply pumped "cold" to the cold side and, via the Megaflow, pumped hot to the hot? pressures should be similar too if megaflow;s put in right...
I have simlar (from a private supply) with a draper =A380 booster pump strill going strong 5+ yrs on buffer tank is a 1500litre ex food container, no megaflow tho, hot from plate heat X in heat bank but should be similar.
Jim K
That's certainly a good value solution. I was concerned about fault conditions and over pressuring the H/W cylinder, with a pump on the h/w outlet you could use a cheapie grade 3 cylinder.
If the buffer tank is a ground level, how do you get initial flow to get the pump running as from what I gather, you need some kind of seed flow to trigger a sensor and activate the pump.
spose depends what "mains pressure" Megaflows are designed for?
. draper (and all others I looked at) jobby has an air pressurised diaphragm in a small attached say 24litre metal "cylinder" that maintains static pipe pressure at 3 or whatever bar, once a "tap" opens, pressure switch susses drop after a few litres come out, and pump kicks in and overruns after tap closed til pressure switch on cyl switches it off
Jim K
Unvented cylinders will have PRV on the inlet anyway, and most pumps won't get up to the limit of the cylinder (not sure what the megaflow one is set at, but the one on my unistor is 3.5 bar)
They do negative head pumps if required...
I'm trying to save the guy some money ;-).
IMO a megaflow is wasted for a stored water installation:
150l megaflow & ancillaries 800quid (more?) cold side push pump 100quid (from your figure) Tot 900150l grade 3 cylinder (lowest pressure rating) 150quid hot side suck pump 100quid (est) Tot 250
Ok, a second pump will be required to pressurise the cold feed if it moves to a totally stored water solution so 350quid tot but if hot and cold isn't being drawn from the mains at the same time then the cold pump may not be required.
1/3 of the megaflow soln which can't be bad.
V useful to know, thank you.
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