Submerged Ballcock Valve

[mc2fool]

We have both a gutter-fed water butt and a regular mains water tap in our garden, and I'm thinking of putting in an automatic irrigation system for some of our beds which I'd prefer to run off the water butt. E.g. this one.

Now the problem with that, of course, is that if there's a dry period the water butt might run out, so I'm thinking of installing a toilet ballcock valve around a third of the way up in the butt and attaching it to the mains water supply, so if the butt drains to below a third full it'll get automatically topped up to that level from the mains supply.

All sounds straightforward enough, but it will mean that when it then rains and the butt fills up with rainwater to the top, the ballcock and valve, being just around a third of the way up, will be totally submerged. Indeed, it'll probably be like that most of the time.

So, is the ballcock and valve being submerged likely to be or cause any problems?

[richlist]

No, it will work.

[bungeejumper]

This might be one of those situations where a plastic cistern valve would be better than a brass one? (Or replace any steel bits you find in the brass valve.)

I'd be impressed if a water butt produced enough rainwater to keep a bed watered for more than a day or so. But it'll certainly make a contribution. Make sure everything's hunky dory before you go off on holiday leaving it connected up. You wouldn't want to come home to a huge water bill and a flooded garden.

BJ

[jfgw]

Connecting a submerged ball-cock directly to the mains water supply is not to be advised.

There are a few risks involved:

Immediate disconnection if your water company finds out;
Prosecution if your water company finds out;
Contamination of the public water supply due to backflow if there is a fault with the supply;
Illness/death of you and your neighbours if the public water supply gets contaminated.

Ok, that last one is probably very unlikely. Faults do occur and backflow from your water butt to the public water supply would be possible, however.

You are meant to notify your water company before installing a garden watering system unless it is designed to be hand-operated. (A rainwater-fed only one is outside the scope of the water regs.)

If the butt is fed from a cistern or tank (rather than the mains) via its own pipe, you should be ok (type AUK1 air gap).

Connecting to the mains gets expensive. A float valve with the outlet above the spillover level of the butt would be needed. One with a drop arm would get you some of the way, https://www.tanks-direct.co.uk/water-ta ... float.html . These look suitable, https://www.heatingandprocess.com/keraf ... improvise/ .

Julian F. G. W.

[mc2fool]

I'd be impressed if a water butt produced enough rainwater to keep a bed watered for more than a day or so.

It's a 250 litre butt and the beds aren't that big. I've not properly measured it but I can water the beds quite a few times by hand with a hose from the butt. The RHS says:

"As a general guide, up to 24 litres per sq metre (5.2 gallons per 10 sq ft) every seven to 10 days will be sufficient to maintain plant growth." https://www.rhs.org.uk/advice/profile?PID=312

So by that our 250 litre butt should be enough for 10m2 for a week. We'll see.

If the butt is fed from a cistern or tank (rather than the mains) via its own pipe, you should be ok (type AUK1 air gap).

Actually, that is the case.

[Lootman]

Contamination of the public water supply due to backflow if there is a fault with the supply;
Illness/death of you and your neighbours if the public water supply gets contaminated.

Ok, that last one is probably very unlikely. Faults do occur and backflow from your water butt to the public water supply would be possible, however.

There are special valves you can fit which prevent backflows. When I had a garden irrigation system installed the contractor insisted on using them to avoid that risk.

The problem I had with using water butts is that they tend to overflow when you don't need rainwater, and then when there is a drought they don't have any water in them anyway. Or the local council will implement a hosepipe ban, which will also apply to irrigation systems.

But I have changed my mind about their value after last summer when my lawn went a yellow-brown colour. One thing that helped was a 50 litre a day dehumidifer in my basement. It made the basement much more pleasant to be in and produced copious amounts of water for the garden (or in winter for flushing the loo).

[Urbandreamer]

Connecting a submerged ball-cock directly to the mains water supply is not to be advised.

There are a few risks involved:

Immediate disconnection if your water company finds out;
Prosecution if your water company finds out;
Contamination of the public water supply due to backflow if there is a fault with the supply;
Illness/death of you and your neighbours if the public water supply gets contaminated.

Julian F. G. W.

You are, or were right. However non-return valve are now sold quite cheaply and in fact are supposed to fit them when fitting an outside tap. Modern outside taps now often have them built it, though in this case you would need a inline one.

ie
https://www.toolstation.com/double-chec ... KoQAvD_BwE
explained here
https://en.wikipedia.org/wiki/Double_check_valve

I would be more concerned that most ball valves are not intended to be submerged and that the head of water could either crush the float or force water into it stopping it floating. You would also have to consider the fact that cold weather could cause ice damage to the valve assembly.

I suggest that a cheaper simpler solution would be to increase the amount of water stored so that rain water is enough. To do this simple get a second butt and connect them together at the bottom

[Imbiber]

Contamination of the public water supply due to backflow if there is a fault with the supply;
Illness/death of you and your neighbours if the public water supply gets contaminated.

Ok, that last one is probably very unlikely. Faults do occur and backflow from your water butt to the public water supply would be possible, however.

There are special valves you can fit which prevent backflows. When I had a garden irrigation system installed the contractor insisted on using them to avoid that risk.

The problem I had with using water butts is that they tend to overflow when you don't need rainwater, and then when there is a drought they don't have any water in them anyway. Or the local council will implement a hosepipe ban, which will also apply to irrigation systems.

But I have changed my mind about their value after last summer when my lawn went a yellow-brown colour. One thing that helped was a 50 litre a day dehumidifer in my basement. It made the basement much more pleasant to be in and produced copious amounts of water for the garden (or in winter for flushing the loo).

50 litres a day!!!
Over 2 litres per hour, that's industrial.

[Lootman]

Contamination of the public water supply due to backflow if there is a fault with the supply;
Illness/death of you and your neighbours if the public water supply gets contaminated.

Ok, that last one is probably very unlikely. Faults do occur and backflow from your water butt to the public water supply would be possible, however.

There are special valves you can fit which prevent backflows. When I had a garden irrigation system installed the contractor insisted on using them to avoid that risk.

The problem I had with using water butts is that they tend to overflow when you don't need rainwater, and then when there is a drought they don't have any water in them anyway. Or the local council will implement a hosepipe ban, which will also apply to irrigation systems.

But I have changed my mind about their value after last summer when my lawn went a yellow-brown colour. One thing that helped was a 50 litre a day dehumidifer in my basement. It made the basement much more pleasant to be in and produced copious amounts of water for the garden (or in winter for flushing the loo).

50 litres a day!!! Over 2 litres per hour, that's industrial.

That's the maximum rating of the device. If humidity is lower then the water extraction rate will be lower. It gets the relative humidity down from 65/70 to 45/50, which makes a big difference to how healthy the space feels, and it doubles as a supply of clean, cold water.

It stands about a metre high and weighs about 20 kg.

[88V8]

One thing that helped was a 50 litre a day dehumidifer in my basement.....it doubles as a supply of clean, cold water.

We have two in our somewhat damp cottage. They incorporate a refrigeration compressor. The 50 litres is the rated maximum. Doesn't produce much water in the summer though.

V8

[sg31]

One thing that helped was a 50 litre a day dehumidifer in my basement.....it doubles as a supply of clean, cold water.

We have two in our somewhat damp cottage. They incorporate a refrigeration compressor. The 50 litres is the rated maximum. Doesn't produce much water in the summer though.

V8

Wouldn't it be better to stop the damp?

I've renovated a lot of properties over the years and always found a way to make them structurally dry. Sometimes it is an expensive process but not always. I know it's off topic for this thread but I am interested in why your cottage is so damp.

(If it's listed that can be a problem.)

[jfgw]

You are, or were right. However non-return valve are now sold quite cheaply and in fact are supposed to fit them when fitting an outside tap. Modern outside taps now often have them built it, though in this case you would need a inline one.

Unfortunately, a non-return valve is not considered sufficient for this application.

Different types of non-return valve, as well as other methods, are used to prevent mains tap water (fluid category 1) from being contaminated with water of a higher fluid category.

The simplest type of non-return valve is the single check valve. This is just a single one-way valve. Obviously, if it jams open, it will allow contamination so it is only suitable where there is no risk to health (fluid category 2), e.g., hot water or water that has passed through a domestic water softener.

A double-check valve is simply two one-way valves in one fitting. If one fails, the other should still provide protection. These can be used where the health hazard is low (fluid category 3) such as the primary heating circuit (radiators etc.) in a house. Note that this includes "Hand held fertiliser sprays for use in domestic gardens"[1] and "Domestic or commercial irrigation systems, without insecticide or fertiliser additives, and with fixed sprinkler heads not less than 150mm above ground level"[loc.cit.]

An RPZ valve (reduced pressure zone valve) is good up to fluid category 4 (significant health hazard). This type of valve is not normally installed in domestic premises and must be inspected annually. Fluid category 4 includes "Mini-irrigation systems without fertiliser or insecticide application; such as pop-up sprinklers or permeable hoses."[2].

There is no valve suitable for protection against fluid category 5 (serious health hazard) back pressure although a pipe interrupter may be used where there is just a back-syphonage risk (such as a urinal). Category 5 includes kitchen sinks, toilets and grey water applications. It also covers many commercial, laboratory, medical, industrial, etc. uses. Toilets have type AUK1 "Air gap with interposed cistern" backflow prevention and sink tap outlets must be above the spillover level of the sink by a specified amount.

While writing this, I have found this publication which is relevant:
https://www.wras.co.uk/downloads/public ... guide.pdf/
From page 7:

What sort of risk are alternative waters?
Essentially all alternative water supplies must be considered a fluid category 5 risk, that is to say it poses a serious health hazard.
...
What backflow protection is required for the mains water back-up supply?
Fluid category 5 protection is required and can only be achieved through the installation of either a Type AA, AB or AD air gap, or through the use of a Type DC pipe interrupter (a device which incorporates an air gap), to separate the mains water supply and the alternative water system. The most common methods are through a Type AA or AB air gap.It must be noted that no mechanical devices are capable of protecting against this level of risk. Therefore no direct or removable cross-connections are allowed

A type AA air gap is where the outlet from the inlet valve is above the spillover level of the cistern (by 20mm or twice the internal diameter of the pipe, whichever is greater). AB is similar except that the cistern has a weir overflow. AD uses an injector where the water is squirted horizontally into the inlet of the cistern.


Julian F. G. W.

References:
[1] ANON, Water Regulations Guide. 2nd ed. WRAS publications, 2000. p.6.2.
[2] ANON, Water Regulations Guide. 2nd ed. WRAS publications, 2000. p.6.3.

[jfgw]

One other point concerning outside taps. Mention was made of taps which incorporate double check valves. These are not normally acceptable for fitting outside as they are prone to frost damage. The only exception is to upgrade an existing tap where the tap was originally legally installed before the regulations required a double check valve, where it is impractical to fit such a valve indoors.

A double check valve is required for any outside tap which will be used with a hose. A double check valve is always required if the tap has a hose union even if it is just used for filling buckets.

Julian F. G. W.