Fitting a float valve to a water tank

[jamieled]

I have a float valve for our water tank, used for our private supply:

 

It has two plastic nuts on the brass thread. I am assuming that one nut ends up on either side of the tank wall, but that doesn't seem like it would give a great seal. Then again, maybe it doesn't need to as the tank water level shouldn't reach the level of the valve inlet.

 

Any insights from those in the know?

[Jeremy Harris]

Yes, just one nut either side.  No, they don't provide a totally watertight seal, but they shouldn't need to, as the overflow pipe will be lower.

 

As an aside, my preference is to use magnetic servo float valves for this job, as they are a heck of a lot more reliable, and are pretty foolproof, as there is no exposed float, lever arm, moving valve piston etc, they are essentially identical to a diaphragm operated solenoid valve but with the solenoid replaced by a magnet within a float, with that float inside a tube, so it can't get fouled up on anything.  Here's an example of one:

 

https://www.bes.co.uk/abertax-magnetic-water-inlet-valve-21341

 

[jamieled]

@JSHarris many thanks, as well as the tip about the servo valve. Hadn't come across that before.

[Jeremy Harris]

1 minute ago, jamieled said:

@JSHarris many thanks, as well as the tip about the servo valve. Hadn't come across that before.

 

 

I found them by accident, years ago, when we had a really difficult to get at header tank in the loft, that made adjusting the ball cock a job for a contortionist.  The Abertax valve just worked out of the box, and was dead reliable.  It also has a very quick shut-off when the right level is reached, with none of the slow dribbling you sometimes get from a ball cock.

[Danny68]

10 hours ago, jamieled said:

I have a float valve for our water tank, used for our private supply:

 

It has two plastic nuts on the brass thread. I am assuming that one nut ends up on either side of the tank wall, but that doesn't seem like it would give a great seal. Then again, maybe it doesn't need to as the tank water level shouldn't reach the level of the valve inlet.

 

Any insights from those in the know?

That particular  valve is not compliant anymore ,not enough  air gap 

[jamieled]

Compliant with what?

[Jeremy Harris]

No issue with compliance with anything, as by definition any vented tank on a water system cannot contain potable water, so any possible issue with contamination from a gap not being sufficient, or from a backflow risk, will be dealt with by the downstream filtering and disinfection system that will be required.

 

 

[ProDave]

6 minutes ago, JSHarris said:

No issue with compliance with anything, as by definition any vented tank on a water system cannot contain potable water, so any possible issue with contamination from a gap not being sufficient, or from a backflow risk, will be dealt with by the downstream filtering and disinfection system that will be required.

 

 

I get the impression this is for potable water on a private supply.

 

I can think of at least 3 such private supplies that I have seen that use a storage tank. However I question is shutting off the feed when full is the correct thing with a stored potable water supply?

 

All the ones I can recall, the tank is there to maintain a buffer as the source is only a low flow. But instead of shutting off the input when full, the tank keeps on getting fed, and deliberately overflows to somewhere safe, so the water is not sitting stagnating.

 

Perhaps some more details of the overall system from @jamieled

[jamieled]

The tank is our hill tank for raw water. From there I will bury a 32mm mdpe pipe to our treatment shed and from there to the house (5m away). Because I'm using UV treatment  I don't plan on storing any significant quantity of potable water.

 

I had been considering whether to run water constantly through the raw water tank, but decided it was probably unnecessary. It's a bit tricky as the tank is not near the source so there is nowhere obvious to discharge to. Otherwise I could install an outlet into the ditch near our house and take a branch off the 32mm and use that to keep water running through the system.

[ProDave]

So why not have the tank close to the source so it can overflow constantly back to the source, and then a longer pipe to the house?

[Nickfromwales]

MDPE is cheap as chips. Run two pipes, one up, one back as ‘recirc’ ?

[Jeremy Harris]

9 hours ago, ProDave said:

I get the impression this is for potable water on a private supply.

 

I can think of at least 3 such private supplies that I have seen that use a storage tank. However I question is shutting off the feed when full is the correct thing with a stored potable water supply?

 

All the ones I can recall, the tank is there to maintain a buffer as the source is only a low flow. But instead of shutting off the input when full, the tank keeps on getting fed, and deliberately overflows to somewhere safe, so the water is not sitting stagnating.

 

Perhaps some more details of the overall system from @jamieled

 

 

On a private supply, water doesn't become potable until it has been treated, so water held as raw water in a vented tank is still raw water, much the same as that in a reservoir.  As such, there aren't any particular requirements that apply, other than common sense ones, like keeping animals and insects out as far as possible.

[jamieled]

9 hours ago, ProDave said:

So why not have the tank close to the source so it can overflow constantly back to the source, and then a longer pipe to the house?

The main reason is that it's extremely difficult to get a tank close to the intake. Not impossible, but it would have required a lot of tree felling over about 300m distance, then getting a decent sized digger in to do enough work to allow a forestry forwarded or similar access to the intake with the tank.

 

The second reason is that from the intake to the tank the pipe cannot be well buried, but the ground from the tank to the house is better. So I hope the tank can provide a bit of buffer in really cold spells.

 

 

[ProDave]

11 minutes ago, jamieled said:

 

The second reason is that from the intake to the tank the pipe cannot be well buried, but the ground from the tank to the house is better. So I hope the tank can provide a bit of buffer in really cold spells.

 

 

More reason to keep the water in the feed pipe moving, very unlikely to freeze if moving.

 

I would be looking for somewhere to overflow to to keep a constant flow.

[jamieled]

I agree. As there's nowhere obvious for an overflow near the tank I think I will just discharge into a ditch / small burn near the house by running water through the supply pipe constantly. This winter might provide a useful testing opportunity.

[Ed Davies]

Water regulations don't apply to a private supply, anyway.

 

BC and/or EH [¹] might impose similar conditions but they'll be happy with equivalent levels of safety, not insisting on to-the-letter compliance. Mine were quite happy with my proposed design for a rainwater supply once I accepted some labelling requirements from BC and  made it clear to EH that I wouldn't be preparing food for the public, i.e., not running a B&B or anything like that.

 

EH sent me a leaflet saying that I should provide 200 (IIRC) litres of water per person per day on the assumption that each bedroom was occupied by two people. I replied that, yes, I'd seen a document like that before but thought it was unreasonable as that isn't how the house is designed to be occupied and that 200 litres/peep/day was a lot more than needed. I referenced a Navitron forum thread about people's actual water usage with different levels of effort to reduce. They accepted that and asked if they could come to have a look at the system once it was installed, for their own education.

 

[¹] Environmental Health.

[Ed Davies]

Maybe not applicable to @jamieled's situation but wouldn't an accumulator tank be better in a case like this as it'd preserve the pressure from the head of water from up the hill?

[ProDave]

7 minutes ago, jamieled said:

I agree. As there's nowhere obvious for an overflow near the tank I think I will just discharge into a ditch / small burn near the house by running water through the supply pipe constantly. This winter might provide a useful testing opportunity.

You won't want a constant run off from your supply pipe as that will kill your water pressure.

 

Either run a supply pipe and a separate overflow pipe, or a high tech solution a level sensor and a solenoid operated drain valve when the tank gets "full"

[jamieled]

@Ed Davies, it's interesting that the BCO and EH took that view on your supply. Even as a type B supply under the 2006 regs (which we also are) there is usually quite a big of work convincing the LA the supply is adequate (and I think we must be in the same region?).

 

I have been considering the need for an accumulator and haven't ruled it out. As you might have concluded from this thread, I don't have things highly planned so it's a bit of work in progress!

[jamieled]

9 minutes ago, ProDave said:

You won't want a constant run off from your supply pipe as that will kill your water pressure.

Useful point, thanks, I may have an old length of mdpe I can use for this.

 

[Ed Davies]

9 minutes ago, jamieled said:

and I think we must be in the same region?

 

As in Highland? Are you near Beauly or am I thinking of somebody else?

[Jeremy Harris]

FWIW, BC here wanted me to provide the certificate from EH that the water had been tested and met the required standard for drinking water.  It was one of the few bits of paper they actually took any interest in.

 

We don't have open storage, but pump the water from the borehole. through an oxidisation system (to precipitate "clear" ferrous iron as ferric oxide), to a pair of 300 litre pressure vessels, then a back washable sand filter, to the house potable supply, where we have a UV disinfection unit as a backstop way of being fairly confident there are no bugs in the water.

[jamieled]

@Ed Davies,That's right, maybe 15-20 miles from Beauly.

Edited September 24, 2019 by jamieled
Clarity